Download Weather and Climate of the Reno-Carson City

Weather and Climate of the
Reno-Carson City-Lake Tahoe Region
Nevada Bureau of Mines and Geology Special Publication 34
Photo by Mark Vollmer
Photo by Jack Hursh
Pyramid Lake as seen from Thunderbolt Bay with the snow-covered Pah Rah Range and mountain lee
wave clouds in the distance.
Truckee Meadows Remembered historical ranch outbuilding display at Bartley Ranch Park, Reno,
late December 2004.
Cover photo: Mountain lee wave (lenticular) clouds, with rotor clouds beneath, seen at sunset from U.S. Highway 395
south in Reno. Photo by Kris Ann Pizarro.
Nevada Bureau of Mines and Geology
Special Publication 34
Weather and Climate of the
Reno-Carson City-Lake Tahoe Region
Brian F. O’Hara
Meteorologist
National Weather Service, Reno, Nevada
Gary E. Barbato
Senior Service Hydrologist
National Weather Service, Reno, Nevada
John W. James
Former Nevada State Climatologist
and Professor Emeritus
Department of Geography
University of Nevada, Reno
Heather A. Angeloff
Research Assistant, Nevada State Climate Office
Climatologist/Staff Scientist, Western Regional Climate Center
Tom Cylke
Senior Meteorologist
National Weather Service, Reno, Nevada
2007
In memory of
John W. James
1933–2007
University of Nevada, Reno
College of Science
Mackay School of Earth Sciences and Engineering
Contents
Overview
Introduction
Convective Weather 48
Thunderstorms 48
Thunderstorm wind gusts
Dry microbursts 49
Hail 50
Tornadoes 50
Funnel clouds 51
Dust devils 51
Lightning 51
3
5
Temperature 7
Historic heat waves 13
Historic cold periods 16
Degree days 18
Temperature inversions and air pollution
Growing season and frost 21
19
Wildfires
Precipitation 23
Rain 23
Snow 25
Lake effect snow 27
Historic snowstorms 28
Snow cover 31
Historic winters 32
Ice storms 35
Humidity 36
Fog 36
Freezing fog (pogonip, rime)
Drought and Evaporation
Drought 39
Evaporation 40
49
52
Floods 54
River floods 55
Largest historical floods in western Nevada
and the eastern Sierra Nevada 56
Flash floods 64
Flood frequency in the Truckee, Carson, and
Walker river basins 67
The top 25 weather-related events in the region
since 1850 68
38
Acknowledgments
39
References
Glossary
Wind 42
Washoe Zephyr 42
Mountain lee waves 46
Synoptic-scale wind events 47
Dust storms and sandstorms 47
72
74
77
Appendix A. Weather station history
Reno 81
Carson City 82
Tahoe City 82
81
Dedicated to the employees (past and present) of the National Weather Service (NWS) Forecast Office in
Reno, Nevada, and to the employees of the NWS (and before that the U.S. Weather Bureau) nationwide.
Their selfless service has benefited the American public for well over a century. Without the data that
they collected and archived, the writing of this publication would not have been possible.
2
Overview
by John W. James
There is great diversity in the Reno-Carson City-Lake
Tahoe region’s climate due to large differences in elevation, topography, and the proximity of the region to the
eastern Pacific storm track (terms in bold text are defined
in the glossary). The location of the jet stream over
northern California and Nevada during the winter causes a
mid-winter precipitation maximum over the region. There
are actually two sources of moisture during the warmer
half of the year (which is generally the drier season) and
one source during the colder half of the year (the wet
season in most of Nevada). The sources during the warmer
part of the year (June through September) are the Gulf of
California (and the adjacent eastern Pacific Ocean west of
Baja California) and the Gulf of Mexico. The eastern
Pacific is the primary breeding ground for rain and
snowstorms that affect the state during the colder half of
the year. Also, drying westerly flow down the eastern
slopes of the nearby Sierra Nevada tends to add to summer
stability and dryness. In general, precipitation ranges from
as low as 5 inches in the valleys to as much as 50 inches
along the upper parts of the Carson Range and the Lake
Tahoe basin, the wettest area of Nevada. For example, the
greatest water year precipitation total, 96.91 inches, fell at
Tahoe Meadows, near Mt. Rose, in 1982–83, at the 8500foot elevation. As much as 37 inches of precipitation (rain
plus water equivalent in snow) has fallen in one month at
Tahoe Meadows in both January 1969 and February 1986,
with a record one-month snowfall of 199 inches in January
1916 at Marlette Lake, just three miles south of Tahoe
Meadows.
Climate has an obvious influence on settlement
patterns, such as settlement for industry, ranching, tourism,
vacationing, and retirement. Precipitation amounts and
distribution, both seasonally and annually, are important
for water needs, but are a special concern for certain
settlement patterns (e.g., irrigated farming and waterrelated industry, and water use for domestic and recreational purposes).
Sunshine is not only an important factor for health, but
it also lends promise as an alternative energy source. The
region ranges from 60 to 70% of the possible sunshine
hours in winter and 80 to 85% in summer. Wind can be
welcome on a hot day, but it can create dangerous conditions during a mid-winter cold spell. Each of these factors
is an important part of the area’s climate.
About two-thirds of the average annual precipitation of
the region occurs from November through March, with the
three summer months (June, July, and August) contributing
less than 10% of the annual total. Average annual snowfall
is light in the valleys of western Nevada (25–45 inches),
but up to 350 inches is common in the higher elevations of
the Sierra Nevada and the Carson Range. This is normally
the snowiest area of Nevada, and the 15 to 20 ski areas in
and adjacent to the Lake Tahoe basin are evidence of that.
The heavier snowfall of the Sierra Nevada can make travel
in the mountainous area between Lake Tahoe and the cities
of Reno and Carson City difficult in wintertime, although
road crews try to keep main highways clear as much as
possible.
Water deficits are common, especially in the more arid
areas. For example, average annual precipitation is about
7½ inches in Reno, about 10 inches in Carson City, and
about 20 inches at Glenbrook in the Lake Tahoe basin.
Valleys average 40 to 50 days of measurable precipitation
per year, whereas the Carson Range averages up to 80 days
per year.
The Reno-Carson City area also has the mildest
wintertime temperatures in the northern half of Nevada.
These milder temperatures are due to a prevailing westerly
airflow and the distance from the colder air masses that
invade Nevada from the northeast. Temperature inversions
are prevalent much of the year due to optimum nighttime
cooling conditions and topography, wherein cold air drains
down to valley floors on most clear, calm nights. This is a
problem at times of high pressure stagnation, especially
during winter in urban areas, as air pollutants are trapped
by the cooler valley floor temperatures. The low sun angle
and lack of storminess allow for little heating and/or wind
to break the inversion.
Extremes of cold or heat are not as prevalent here as
they are in other parts of Nevada. Winter nights rarely fall
below zero, and days are usually above freezing, except in
the mountains. Summer days are warm, but nights
pleasantly cool, with just a few days near 100ºF likely
every year in the valleys (Reno’s all-time high of 108°F
occurred in July 2002). Around Lake Tahoe, summertime
highs are usually in the 70s and 80s in most areas and
evening lows are generally in the 30s and 40s. The frostfree season lasts about 120–130 days in the valleys, but
only 80–95 days or less in the Lake Tahoe basin, where
late spring and early fall frosts are common.
Occasionally during the winter season, strong
downslope winds may reach destructive levels. This was
the case for example, in November 1981, when an
unusually high 101 mph (miles per hour) wind gust was
recorded in southwest Reno. This was associated with a
powerful winter storm from off the Pacific that caused
significant damage in the Reno area.
Air conditioning can be an important comfort factor
during summer days in the valleys of western Nevada as
temperatures frequently rise to 90°F or higher. It is not
needed as much at Lake Tahoe, however, because days
over 90°F are infrequent. Wintertime heating requirements
are more important, with the abundance of sunshine
allowing for solar devices to be more useful in this region.
Heating requirements are stringent in the Lake Tahoe basin,
not due to extreme cold, but rather because of a combination of precipitation, wind, and cloud cover during storms.
3
Photo by Mark Vollmer
Thunderheads build over Lake Tahoe's south shore, as seen from Tahoe Rim Trail near Spooner Summit.
In a Nutshell
• Sunshine is abundant throughout the year: 60–70%
of possible sunshine in winter and 80–85% of
possible in summer.
• The Reno-Carson City-Lake Tahoe region is the only
one in Nevada with a pronounced wintertime
precipitation maximum (two-thirds falls from
November through March).
• Frost-free season is 120–130 days in the valleys, but
only 80–95 days or less in the Lake Tahoe basin.
• Annual precipitation averages 5–12 inches in valleys
and 40–50 inches in the Carson Range on the east
side of the Lake Tahoe basin.
• Strong winds of 70 mph or more associated with
winter storms occur every winter.
• Annual snowfall averages 25–45 inches in valleys
and up to 350 inches in the Carson Range (the
snowiest area of Nevada).
It should be noted that the Reno weather observation
site has been staffed by U.S. Weather Bureau (USWB) and
later National Weather Service (NWS) staff from its
inception in November 1905. Thus a fairly complete record
of weather and climate data is available for Reno for the
past 100 years. The weather observation sites at Carson
City and Tahoe City have not been staffed by USWB and
NWS employees, but by volunteer cooperative weather
observers. The data that they collected (although just as
valuable) was generally restricted to temperature, precipitation, and snowfall.
This should be kept in mind when studying the data in
the following document. Data for wind speed and direction,
relative humidity, occurrences of fog, and occurrences of
thunderstorms have not been collected at Carson City and
at Tahoe City, so the figures for these data below will only
reflect data that has been collected at Reno. Figures for
temperature, precipitation, and snowfall, however, will
reflect data from all three sites. Changes in the location of
weather observation sites over the years at Reno, Carson
City, and Tahoe City are described in Appendix A.
• Snow normally covers the ground above 7000 feet in
the Carson Range from about November to April and
does cause some travel impedances during storm
periods.
• Because of the relatively dry summers there are
typically only 40–50 days per year with precipitation
in the valleys, 70–80 days in the mountains.
• The region has fewer temperature extremes than are
found in the remainder of Nevada.
• Air conditioning is not necessary but does add to midsummer comfort. Winter heating is necessary, but
abundant sunshine makes possible solar heating
devices.
• Winter nighttime temperature inversions are a
problem concerning air pollution in urban areas,
especially along valley floors.
4
Photo by Chris Ross
The Stone Mother or Squaw and Basket formation, Pyramid Lake. This
photo, taken in the early 1980s, shows the tufa formation surrounded by
water just south of the Pyramid on the east side of Pyramid Lake .
Introduction
by Brian F. O’Hara and Heather Angeloff
east” (Smith, 2000). The lake formed after lava from Mt.
Pluto dammed the north end of the basin approximately 2
million years ago. Numerous other geologic faults are
located throughout western Nevada and the eastern Sierra,
and close to 30 earthquakes of magnitude 4.0 or greater on
the Richter Scale have been reported in the area within the
last 150 years. The number and strength of earthquakes
generally decreases as you move east from the Sierra
Nevada, with the vast majority of Nevada earthquakes
being recorded in the western half of the state.
Sagebrush is the dominant plant in the dry valleys of
the western Great Basin. However, as you climb the Carson
Range the vegetation changes to a more alpine type. The
first trees encountered are Jeffrey pine, interspersed with
montane chaparral; and higher up in elevation you find
white fir. On the other side of the Carson crest, on the
eastern side of Lake Tahoe, you also find mainly Jeffrey
pine and white fir. On the more thickly forested west side of
Lake Tahoe, the trees include Jeffrey, sugar, and ponderosa
pines; white fir; and incense cedar at lower elevations.
Higher up are found Jeffrey, lodgepole, and western white
pines; Sierra juniper; and red fir (Howald, 2000).
The Truckee River begins at Tahoe City and winds its
way between the Carson Range and Peavine Mountain,
flows east through the valley known as Truckee Meadows,
and then empties into Pyramid Lake northeast of Reno.
Between the Carson Range to the west and the smaller
mountains to the east a valley extends from the Truckee
Meadows south through Carson City to Minden and
Gardnerville. This valley, with Reno as its hub, has the
largest population density in Nevada outside of Las Vegas.
Even though they are close to one another geographically,
the climate of the Reno and Carson City area is quite
different than the climate of the Lake Tahoe basin. Reno
and Carson City are located at the base of the eastern
slopes of the Sierra Nevada in the western part of the
physiographic region known as the Great Basin. The Great
Basin extends from the crest of the Sierra Nevada east to
the Wasatch Front in central Utah (Figure 1). It is a closed
basin because no rivers or streams flow out of it. Most
surface water is lost through evaporation. The Great Basin
is a high desert with an average elevation of 5000 feet
above sea level. By contrast, the Lake Tahoe basin is an
alpine basin with Tahoe City receiving ten times the
snowfall that Reno and Carson City receive. The Lake
Tahoe basin is cooler because it is at a higher elevation and
it has more precipitation and higher humidity than do the
valleys just east of the Sierra Nevada.
Actually, the mountains immediately west of Reno and
Carson City belong to the Carson Range, a spur of the
Sierra Nevada. To the southwest of Reno, Slide Mountain
(9694 feet in elevation) and Mount Rose (10,776 feet) are
part of the Carson Range. Just to the northwest of Reno is
Peavine Peak (8260 feet), and southeast of Reno are the
Virginia Mountains with peaks over 7000 feet. South of the
Virginia Mountains, east of Carson City, are the Pine Nut
Mountains with peaks rising to over 9000 feet. The Pah
Rah Range extends to the northeast of Reno with elevations over 8000 feet.
Lake Tahoe lies in a basin that formed when it
“dropped down along faults on either side, while the Sierra
block rose on the west and the Carson Range on the
5
Figure 1. Western Nevada and northeastern California, showing some of the locations mentioned in this publication.
Inset shows map location in relation to the Great Basin.
6
Photo by Chris Ross
Photo taken in alfalfa field on the Pyramid Lake highway. The air temperature was high enough to
allow irrigation spraying from the wheel lines, while the surface temperature was low enough to
freeze the water when it hit.
Temperature
by Brian F. O’Hara
The Reno-Carson City-Lake Tahoe region experiences a
wide range of temperatures on both a daily and a yearly
scale. This is mainly due to the relatively high elevation of
the Great Basin and to the relatively dry air mass typically
over the region throughout most of the year. The Great
Basin has elevations ranging from around 4000 feet in the
valleys to over 10,000 feet in the highest mountain ranges.
Because of these high elevations, incoming solar radiation
over the region is more intense and the air mass near the
ground is less dense than they are at lower elevations.
Thus, there are fewer molecules in the air mass to absorb or
reflect the sunshine passing through. The air also tends to
be quite dry over the region. This means that there is less
water vapor in the air to absorb energy before it reaches
the surface.
Temperatures during the summer months at Reno and
Carson City often reach the 90s during the afternoon and
can even rise to over 100ºF (temperatures are in degrees
Fahrenheit [ºF] throughout this publication). Temperatures
of at least 100º can be expected at least once each summer
and up to five times or more every other summer, on
average. Because of its higher elevation (and proximity to a
large body of relatively cold water), temperatures at Tahoe
City, on the northwest shore of Lake Tahoe, tend to be
cooler than at either Reno or Carson City; afternoon highs
at Tahoe City tend to be 10 to 15° cooler during the
summer. The average high temperatures that can be
expected during July across the eastern Sierra and western
Nevada are shown in Figure 2 on page 9.
The dry atmosphere over the western Nevada valleys
heats up quickly during the day because there is less water
vapor in the air mass to absorb the solar energy passing
through. At night, however, the ground and the air
immediately above it cool rapidly due to the lack of cloud
cover. Heat is radiated very efficiently and the air near the
ground can cool 40° below its afternoon peak. After highs
in the mid 90s, the temperature can drop into the mid 50s
by sunrise. This large temperature range can make the hot
conditions during the afternoon more bearable. Occasionally a light jacket may be needed in the evening even
during mid summer. These temperature ranges are also
experienced at Tahoe City. The average low temperatures
that can be expected during July across the eastern Sierra
and western Nevada are shown in Figure 2 on page 9.
A large daily temperature range is also noticeable
during the winter but it is usually not as large as that
experienced during the summer. This is because the
relative humidity of the air mass tends to be higher during
the winter. As in the summer, the dew point temperature
near the ground may be in the 20s. However, unlike the 90º
temperatures seen during the summer in Reno or Carson
City, afternoon temperatures (even at Tahoe City) during
the winter are closer to the dew point readings. Solar
radiation is absorbed by water vapor in the atmosphere.
Thus, solar energy that is absorbed cannot reach the
ground. Cloud cover is also more common during the
winter as a result of large synoptic-scale storms passing
through the region. This cloud cover tends to keep daytime
7
temperatures at Carson City are similar to those at Reno
but temperatures at Tahoe City (on the west shore of Lake
Tahoe) tend to be 10 to 15° cooler.
Western Nevada skies are relatively clear most of the
year. With the dry atmosphere over the region there simply
is not enough water vapor in the air mass that can condense
into clouds. Reno receives almost 80 percent of the solar
energy that enters the atmosphere (Figure 4). This means
that an average of around 20 percent of the sun’s energy is
absorbed or reflected by molecules in the atmosphere.
Sunshine data are not available for Carson City or Tahoe City.
Figure 5 shows the various sky conditions reported
over Reno throughout the year. It is apparent that days tend
to be sunnier and nights clearer at Reno during the summer
than at any other time of year. This contributes to the larger
daily temperature ranges during the summer than during
the winter. During July, August, and September, skies are
clear two-thirds of the time, and days are cloudy (nearly
complete cloud cover) only two or three times per month.
During the winter, skies are cloudy about half the time and
skies are clear almost a third of the time. Higher relative
humidity and more frequent synoptic-scale storms passing
through the region contribute to the greater cloud cover
during winter.
temperatures from rising as high as they would otherwise,
and it keeps nighttime temperatures warmer because
radiation is not lost to the upper atmosphere as easily as it
would be under clear skies.
Afternoon high temperatures during the winter may be
in the 30s or 40s, both in the western Nevada valleys and at
Lake Tahoe. In the absence of winter storms, skies tend to
be relatively clear during the winter, so afternoon temperatures can rise fairly quickly and the air mass can then cool
considerably at night. Daily temperature ranges during the
winter can be 30° or even 40° because winter afternoon
highs reach the 40s or 50s and then cool down into the
teens or 20s at night at Reno and Carson City (Figure 2 on
page 9).
It is rare for temperatures to fall below zero at night
during the winter in either western Nevada or at Lake
Tahoe. Even with its higher elevation, the water in Lake
Tahoe helps to modify the air mass and keeps temperatures
from reaching the all-time monthly record lows seen at
Reno and Carson City (Figure 2 on page 9). Table 1 and
Figure 3 show normal high and low temperatures and
record high and low temperatures for each month at Reno,
Carson City, and Tahoe City. Table 1 also lists the years in
which the record highs and lows occurred. Monthly
Table 1. Monthly temperatures (ºF) at Reno and Carson City, Nevada, and Tahoe City, California
Jan
Feb
Mar
Apr
May
June
July
Aug
Sep
Oct
Nov
Dec
Record high (year)*
Reno
71
(2003)
76
(1888)
83
(1966)
89
(1981)
98
(1910)
104
(1940)
108
(2002)
105
(1983)
101
(1950)
91
(1980)
77
(1980)
71
(1940)
Carson City
72
(2003)
76
(1972)
81
(1966)
88
(1981)
93
(2003)
101
(1950)
105
(2002)
103
(1972)
103
(1950)
91
(1964)
78
(1960)
75
(1958)
Tahoe City
59
(1990)
60
(1985)
67
(1996)
74
(1981)
81
(1986)
90
(1961)
93
(1934)
94
(1933)
87
(1955)
80
(1933)
70
(1988)
60
(1990)
Normal high (1971–2000)
Reno
45.5
51.7
57.2
64.1
72.6
82.8
91.2
89.9
81.7
69.9
55.3
46.4
Carson City
45.6
50.7
56.6
63.2
71.6
81.2
89.2
87.8
80.2
68.8
54.7
46.2
Tahoe City
40.5
42.0
45.1
51.4
60.1
69.2
77.5
77.0
70.1
60.0
47.9
41.4
Normal low (1971–2000)
Reno
21.8
25.4
29.3
33.2
40.2
46.5
51.4
49.9
43.1
34.0
26.4
20.7
Carson City
21.7
25.4
29.5
33.0
39.7
46.1
50.7
49.1
42.4
33.4
26.4
20.8
Tahoe City
20.1
21.3
24.3
27.7
33.5
39.6
44.7
44.8
39.6
32.3
25.5
20.6
Record low (year)*
Reno
-19
(1890)
-16
(1989)
-3
(1897)
13
(1956)
16
(1896)
25
(1954)
33
(1976)
24
(1962)
20
(1965)
8
(1971)
1
(1958)
-16
(1972)
Carson City
-20
(1949)
-22
(1989)
-5
(1952)
12
(1972)
18
(1967)
27
(1954)
33
(1987)
26
(1968)
20
(1965)
6
(1971)
-4
(1994)
-19
(1990)
Tahoe City
-15
(1916)
-15
(1989)
-6
(1935)
5
(1999)
9
(1974)
24
(2005)
22
(1975)
29
(1957)
21
(1965)
9
(1971)
1
(1931)
-16
(1972)
* Since 1888 at Reno, 1948 at Carson City, and 1914 at Tahoe City.
8
Figure 2. Average high and low temperatures for January and July across the eastern Sierra and western Nevada.
Copyright © 2005, PRISM Group, Oregon State University, www.prismclimate.org. Maps created November 1, 2005.
9
Photo by Mark Vollmer
Figure 13. Average annual precipitation and snowfall across the eastern Sierra and western Nevada. Precipitation map copyright © 2005, PRISM Group, Oregon State University. Snowfall map created by Gary Johnson.
Evening thunderstorm over distant Pine Nut Mountains. View across Washoe Valley and the Virginia Range from the
Mt. Rose Highway. Lights of Washoe City can be seen in the near distance.
10
Photo by John James
Photos by Kris Ann Pizarro
Flow control structure at the outlet of Lake Tahoe into the Truckee River. The lake level occasionally
drops below the outlet during droughts such as the one in 1991 when this photo was taken. See
figure 20 on page 39.
Comparison, Washoe Lake, August 2004 (dry) and June 2006 (full).
11
Photo by Mark Vollmer
Photo by Mark Vollmer
Cirrus clouds over the Truckee Meadows.
Smoke from the Martis Creek wildfire over the Carson Range between Reno and Lake Tahoe, June 2001.
Downtown Reno is in the foreground.
12
Figure 4. Percent of solar radiation entering the
atmosphere that reaches the surface at Reno,
Nevada (1961–2005). The annual average is 79
percent.
High pressure forms over the Great Basin
during the winter. Extensive snow cover cools the
lower atmosphere and helps to strengthen this area
of high pressure (Hill, 1993). The downward motion
associated with this high pressure can keep
pollutants trapped near the surface for days at a
time. The air over western Nevada is cleaner than it
has been in decades past (in part due to a ban on
wood burning, and annual smog checks being
required on automobiles), but temperature inversions can still keep hazy conditions across the
region during the winter, especially in urban areas.
HISTORIC HEAT WAVES
Warm temperatures can be expected each summer
in the valleys of western Nevada. Readings of at
least 100º can also be expected just about every
summer, usually in July or August. However, some
warm periods stand out as particularly severe.
Some of the most impressive heat waves of the last
100 years in the Reno and Carson City areas are
listed below. The Lake Tahoe basin does not usually
experience temperatures as high as those recorded
in the valleys east of the Sierra.
Figure 3. Monthly temperatures (ºF) at Reno and Carson City.
Nevada, and Tahoe City, California.
13
July 1931. This is the sixth warmest July on record
at Reno with a monthly average of 77.4ºF. Eight
days in the last half of the month recorded daily
high temperatures of at least 100º. For six consecutive days (the 18th through the 23rd) the high
temperature was 102º or greater. On the 19th the
high temperature was 105º and on the 20th it reached
106º. This reading was the all-time record high for
Reno until July 2002 when readings on two days
reached 108º. Up at Lake Tahoe it was also warm;
the temperature at Tahoe City reached at least 90º
from July 20 through the 23rd. The 93º reported on
the 20th remains the all-time record high for the
month of July at Tahoe City.
August 1933. For five consecutive days (11th through
the 15th) the daily high temperature at Reno was at
least 100º. The high temperature of 103º on the 13th is
still the record high for that date. At Tahoe City the
afternoon temperature was over 90º for four consecutive days from the 12th through the 15th. The 94º
recorded on the 15th remains the highest temperature
ever recorded at Tahoe City.
July 1959. This was a very warm July with temperatures reaching 100º on seven days in Reno. On six
consecutive days (16th through the 21st) the high was
at least 100º. On July 20 the temperature reached 100º
at Carson City, still the record high for that date. It got
up to 101º on the 11th and this remained the record
high for that date at Carson City until the incredible
summer of 2002. Temperatures dropped into the 50s
at night, making the heat more bearable. At Tahoe
City afternoon highs during this period were around
10° cooler than those experienced at Reno and Carson
City. The weather map for July 18, 1959 is shown in
Figure 6 .
July 1980. Warm weather visited the region in late
July with temperatures reaching at least 100º on seven
consecutive days (21st through the 27th) at Reno. The
readings on the 25th, 26th, and 27th (104º, 104º, and
103º, respectively) are still the all-time record highs
(or tied for the record high) for these dates. At Carson
City the temperature reached 100º on the 22nd and
101º on the 27th. The weather map for July 26 (Figure
6) shows the ridge of high pressure that was over
much of the Intermountain West.
July 2002. This is the fourth warmest July on record,
and the third warmest month ever at Reno. It had been
the warmest ever until July 2003 broke the record.
Temperatures reached at least 100º on six days. On
four consecutive days (9th through the 12th) the high
was at least 101°, and reached 108º on both July 10
and 11, setting new all-time high temperature records
for Reno. Not only was it hot during the day, but it
remained warm at night. From the 10th through the
17th, the temperature never dropped below 61º. On the
morning of the 12th, after the second day of 108º
temperatures, the low was a balmy 74º. The record
warmth during this month at Reno can mainly be
attributed to the abnormally warm minimum temperatures at night. This warmth is the result of the urban
heat island effect. At Carson City new record highs
were set on four days with readings of 100º, 105º,
104º, and 99º on the 9th, 10th, 11th, and 12th, respectively. The 105º reading on the 10th is now the highest
temperature ever recorded at Carson City. Figure 6
shows the surface weather map for July 11, 2002.
Figure 5. Average number of cloudy, partly cloudy, and cleardays at Reno, Nevada (1943–2004).
14
July 2005. With an average temperature of 80.0° this
is the warmest month on record at Reno. The high
temperature for each day from the 12th through the 21st
Figure 6. Surface weather maps for July 18, 1959, 1:00 am EST; July 26, 1980, 7:00 am EST; July 11, 2002, 7:00 am
EST; and January 8, 1890, 8:00 am EST (pressure in millibars reduced to sea level). Maps courtesy of the NOAA
Central Library Data Imaging Project.
15
the 11th and down to -9º on the 12th. After a powerful
storm dropped over 2 feet of snow on Reno (22.5 inches
on the 17th alone) temperatures plummeted. On the
morning of the 20th the recorded low was -11º and on the
21st the temperature dropped to -17º. After a third
snowstorm moved through the region late in the month,
the temperature dropped to -13º on the 31st. This remains
the fifth coldest January on record at Reno.
It was a snowy month at Lake Tahoe with 238
inches of snow being reported at Tahoe City. Ten feet of
snow was on the ground by the end of the month. The
temperature dropped to below zero on six days. On the
11th the morning low at Tahoe City was -14º. The
temperature dropped to -15º on the 30th, and -14º was
reported on the 31st.
exceeded 100º, setting a new consecutive-day record of
10 straight days at or above 100º. The temperature rose
to 104º on both the 12th and the 16th. It was warm
throughout the region. Carson City reported highs in the
upper 90s during this same 10-day period. The temperature there on the 17th reached 100º. At Tahoe City the
afternoon highs were 80º or above from the 11th through
the 20th.
HISTORIC COLD PERIODS
During the winter temperatures can plummet after the
passage of a strong cold front. Temperatures can drop to
below zero at night with readings 20° to 30° below
normal. The cold air mass can remain over the region for
a week or longer. This can be a serious threat to public
safety as public utilities have a difficult time supplying
enough power for heating. The very cold weather can
also cause pipes to freeze, making life even more
difficult. Snow cover can remain for weeks because the
cold air mass does not allow for rapid melting. Even
though cold weather can be expected every winter in the
region, some cold outbreaks can cause incredible
hardship and are remembered for years to come. Some
memorable cold outbreaks are listed below.
January 1937. This was an extremely cold month with
the average temperature on every day except one
(January 14th) below normal at Reno. The average
temperature for the month was 15.8º. The morning low
temperature was below zero on seven consecutive days
(January 7 through 13). The low was -10º on the 7th, -16º
on the 8th, and -14º on the 9th. It remained cold throughout the rest of the month with the morning low on the
20th reaching -12º, and then -14º on the 21st. This is the
second coldest January on record at Reno. It was also
bitterly cold at Lake Tahoe with record low temperatures
being set at Tahoe City. On both the 9th and 21st the
temperature dropped to -14º. The temperature dropped to
-13º at Tahoe City on the 20th. At Boca (5 miles northeast
of Truckee), the temperature fell to -45° on January 20th.
This remains the all-time record low temperature for the
state of California.
January 1890. Cold conditions first hit the region in late
December 1889 when the temperature at Carson City
dropped to -7º on the 29th. The cold weather continued
through January. A bitterly cold air mass moved into the
region early in the month with temperatures dropping to
well below zero at Carson City on four consecutive
nights. On January 6 the low temperature was -10º. The
next morning the low was -17º, and on both the 8th and
the 9th the morning low was an incredible -22°. There
was another report from Carson City of the temperature
dropping to -27º the morning of the 8th. (However, these
readings are not listed in the records because official
readings at Carson City only date from 1948.) At Reno
the morning low on both the 7th and the 9th was -18º. The
lowest temperature for the entire month at Reno occurred
on January 8 when the temperature dropped to 19º below
zero. This reading remains the all-time record low for
Reno for any month. The strong dome of high pressure
over the Intermountain West on January 8, which helped
temperatures drop to record lows, can be seen on the
weather map for January 8, 1890 in Figure 6.
Cold weather was experienced later in the month
when the temperature at Carson City dropped to -4º on
the 22nd. Even colder conditions occurred the last week
of January 1890 as temperatures at Carson City dropped
to -11° on the 27th and -9° on the 28th.
January 1949. A very cold month with an average
temperature of 14.1º reported at Reno. Only three days
during the month had an average temperature greater
than 20º. Each day during the month the average
temperature was below normal. The morning low
temperature was below zero on all but eight days. The
morning low was -10º on the 11th and -11º on the 12th.
The temperature fell to -12º on January 15. Bitterly cold
weather continued through the rest of the month with
lows of -16º on the 25th and -15º on the 26th. Incredibly,
the average minimum temperature for the month was 2.2°! This is still the coldest January on record at Reno.
At Carson City the morning temperature dropped to
-15º on the 4th, -10º on the 17th, -16º on the 25th, and -20º
on the 26th. The -20º reported on the 26th remains the
record low temperature for January at Carson City.
Figure 7 shows the ridge of high pressure that was over
much of the western United States on January 25.
Conditions were not as bitterly cold at Lake Tahoe
during the month. However, the temperature dropped
below zero on five mornings at Tahoe City. The lowest
reading for the month was -6º reported on the 4th.
January 1916. The snowiest month on record at Reno
helped keep average temperatures low. Over a foot of
snow fell at Reno on January 9 and 10. After this storm
system moved through, temperatures dropped to -1º on
16
First half of December 1972. Incredibly cold temperatures were recorded during the first half of December.
This remains the second coldest December on record at
Reno. Low temperatures on six of the days are still the
all-time record lows for those dates. The morning low
at Reno dropped to -12º on the 5th. After a slight
warmup temperatures plummeted. During the second
week of December daily average temperatures were
over 20° below normal. From the 9th through the 11th
average temperatures were over 30° below normal. On
the 8th the morning low fell to -12º. Low temperatures
on the 9th, 10th, and 11th were -16º, -11º, and -15º,
respectively. The -16º on December 9 remains the
record low temperature for the month in Reno. The
high temperature on the 9th was only 6˚ above zero.
This remains the lowest maximum temperature ever
recorded at the Reno airport. The cold front that moved
through the Sierra and western Nevada on January 9
ushered in the incredibly cold air mass (Figure 7).
During the first half of December at Carson City,
the temperature dropped to below zero on six days.
These six readings remain the lowest ever recorded on
these dates. It dropped to -11º on the 5th. As at Reno,
there were a few days of warmer temperatures before
the cold set in again. On the morning of the 9th the
temperature dropped to -14º, and two days later, on the
11th, the morning low was -18º.
Up at Lake Tahoe it was also bitterly cold. For
four mornings, from the 9th through the 12th, record low
temperature readings were set. On the 9th Tahoe City
reported a low of -10º. On the 10th the low was -11º,
and on the 11th the morning low was -16º. On the 12th
the low was still below zero at -4º. The low temperatures for these four days remain the record lows for
these dates at Tahoe City. In fact, the -16º reported on
the 11th is the lowest temperature ever recorded at
Tahoe City.
Early February 1989. An incredible cold outbreak in
early February saw daily average temperatures drop to
almost 40° below normal. In Reno, on the 6th and 7th,
the average temperature was 37° colder than it usually
is during the first week of February. The temperature
on the morning of the 5th fell to -10º. On the 6th the
morning low was -15º, while on the 7th the low fell to
-16°. This is the all-time record low temperature for
February at Reno. It was still bitterly cold on the 8th
with a low of -12º. At Carson City the temperature
dropped to -19º on the 6th, -22º on the 7th, and -17º on
the 8th. The -22º on the 7th is the lowest temperature
ever recorded at Carson City (using official weather
data from July 1, 1948 to present). It was also incredibly cold at Tahoe City during the first half of the
month. On the 6th the temperature dropped to -13º, on
the 7th it dropped to -15º, and on the 8th the morning
low was -13º. The -15º on the 7th is the record low
temperature for February at Tahoe City.
Figure 7. Surface weather maps for January 25, 1949,
1:30 am EST and December 9, 1972, 7:00 am EST
(pressure in millibars reduced to sea level). Maps courtesy of the NOAA Central Library Data Imaging Project.
17
DEGREE DAYS
Many people find it useful to know how much warmer or
colder it is compared to some standard temperature. Utility
companies especially like to have some sort of number to
use in determining how much power may be needed during
periods that are colder or warmer than normal. An index
that has been found useful is “degree days.” Degree days
are based on the difference between 65°F and the average
temperature of a day. The average temperature of a day is
the average of the maximum and minimum temperature for
that day. For example, if a day has a maximum temperature
of 73°F and a minimum of 49°F, its average temperature is
61°F. Degree days are listed as either “heating degree
days” or “cooling degree days,” depending on whether the
average temperature is less than or more than 65°F.
Degree days are calculated for a period of time (a
month, for example) by calculating the differences between
65 and the average temperature of each day in that time
period, and then adding up all the differences for days
averaging above 65°F as cooling degree days, and all of the
differences for days averaging below 65°F as heating
degree days. Heating degree days provide an index of how
much heating is needed to raise the temperature to 65°F,
and cooling degree days provide an index of air conditioning requirements.
Figure 8 and Table 2 show the average number of
degree days recorded at Reno, Carson City, and Tahoe City
for each month. More than 10 times as many heating
degree days as cooling degree days are recorded at both
Reno and Carson City throughout the year (Table 2).
Almost no cooling degree days are recorded at Tahoe City.
Average daily temperatures during the winter are
often 30 to 40° colder than the degree day index base of
65º. High temperatures rarely reach 65º during the winter.
However, during the summer at Reno and Carson City,
even with afternoon readings in the 90s, temperatures can
fall into the 50s at night, causing the average temperature
for the day to approach 65º.
Figure 8. Average number of heating and cooling
degree days at Reno and Carson City, Nevada,
and Tahoe City, California (1971–2000).
Table 2. Average number of heating and cooling degree days at Reno and Carson City, Nevada, and Tahoe City,
California (1971–2000).
Jan
Feb
Mar
Apr
May
June
July
Aug
Sep
Oct
Nov
Dec
Total
Heating degree days
Reno
984
756
683
502
285
91
12
22
130
416
732
987
5600
Carson City
972
755
682
507
306
110
11
27
149
433
733
976
5661
Tahoe City
1076
934
924
763
565
320
142
148
310
585
849
1055
7671
Cooling degree days
Reno
0
0
0
0
11
72
204
164
41
1
0
0
493
Carson City
0
0
0
0
16
68
164
133
37
1
0
0
419
Tahoe City
0
0
0
0
0
2
20
21
4
0
0
0
47
18
Photo by Heather Angeloff
Air pollution trapped under a temperature inversion over the Truckee Meadows.
TEMPERATURE INVERSIONS AND AIR POLLUTION
Inversions over the western Great Basin typically form
in one of two ways. One way is through upper level subsidence. In an area of high pressure, air moves downward
(subsides) and then moves outward when it reaches the
ground. As the air subsides, it becomes warmer and also
tends to dry out. The top of a subsiding layer of air travels
relatively farther through the air mass than does the air in
the lower part of the layer. Thus, this air at higher levels
tends to warm and dry out at a faster rate than does the air
below it. Because of this, the air that is higher up (and
which travels farther) becomes warmer than the air below
it. An inversion that forms from this process is called a
subsidence inversion (Figure 9).
The other method that can cause an inversion is
through radiational cooling near the ground. At night, especially in regions that have dry air near the ground at high
elevations, the ground starts to cool shortly after sunset as
its heat is radiated into the air near the surface. In addition
to the heat that is radiated into the atmosphere, additional
heat is lost as the ground continues to cool during the night,
and the air that is in contact with the ground cools as a result. A cold surface such as snow can cool the air in the
lower layer of the air mass even more effectively than dry
soil can. As a result of these processes, an inversion forms
near the surface. Because this surface inversion is mainly
caused by the loss of heat through the process of radiation
into the atmosphere, it is called a radiation inversion
(Figure 10).
In the past air pollution has been a problem in the Reno
area. Because of the topography of the area, pollution can
remain over the region, sometimes for days at a time. The
area from Reno and extending south to Carson City is situated between the Sierra Nevada and Carson Range to the
west and the Pine Nut Mountains and other mountain
ranges to the east. Because of the surrounding mountains,
upper level winds do not always make it to the surface. The
stagnant condition in the valley allows haze to remain. It
often takes a shift in wind direction such as winds coming
out of the south to mix the stagnant air and move it away.
A cold front can also supply the stronger winds that can
clear the pollution from the area.
One thing that makes pollution so prevalent is the temperature inversions that are common over the area. An inversion is a layer of the atmosphere in which temperature
does not follow its typical cooling pattern with increasing
height. In an inversion, the air temperature increases with
height (or does not decrease as quickly as it normally
does). An air parcel that is forced upward remains cooler
than the temperature of the air mass at that height. As a
result, any rising air parcel remains denser than the surrounding air so it does not continue to rise, but eventually
falls back to the surface. Inversions thus help to keep low
level air near the ground and keep it from mixing with air
at higher levels. This lack of mixing is what keeps the stagnant air trapped near the ground, and helps to keep any air
pollution from mixing out and eventually dissipating.
19
Figure 9. A typical subsidence inversion over the Truckee Meadows.
the “Washoe County AQMD is required by federal and
state law to monitor and collect ambient Air Quality Data
for pollutants deemed to be harmful by the U. S. Environmental Protection Agency (EPA)” (Washoe County Air
Quality Management Division, 2002). The pollutants that
AQMD monitors are: (1) carbon monoxide (CO); (2) ozone
(O3); (3) particulate matter less than 10 microns in diameter, and less than 2.5 microns in diameter; (4) nitrogen
dioxide (NO2); (5) sulfur dioxide (SO2); and (6) lead (Pb).
One of the major constituents of pollution is automobile exhaust. The Reno and Carson City areas have experienced rapid growth during the last 15 to 20 years. The
number of automobiles has increased substantially, but the
physical dimensions of the surrounding topography have,
of course, not changed. Thus, there are more pollutants
being sent into the same amount of air. The AQMD estimates that approximately 94 percent of the CO emissions
in the Truckee Meadows area are from motor vehicles.
Carbon monoxide emissions have decreased during the last
15 years. During the early 1990s there were sometimes 15
Throughout the year, the air near the ground cools at
night so radiation inversions are common. However, unless
there is snowcover to keep the surface cold, the inversion
dissipates during the day as the ground is heated, and
mixing of the air can result. If high pressure is over the
region, the descending air within this high can cause a
subsidence inversion to form aloft. This type of inversion
can be created at any time of year since it relies on the
presence of an area of high pressure. The stable air associated with these inversions resists mixing, so the air mass
does not change. Even if upper level winds are strong they
tend not to mix down through this stable layer. Larger
pollutants (such as those from dust storms and wildfires)
eventually fall to the ground. However, smaller particles in
gaseous emissions (such as from factories and automobile
exhaust) remain in the atmosphere (Graedel and Crutzen,
1997).
The Washoe County Air Quality Management Division (AQMD) monitors the level of pollutants in the atmosphere over the Reno area. According to an AQMD report,
Figure 10. The development of a typical nighttime radiation inversion over the Truckee Meadows.
20
to 35 moderate to unhealthy CO days per year. By 2001 the
number had dropped to fewer than five days per year.
Ozone is another pollutant that can cause problems for
people. Ozone is formed from the chemical reaction between hydrocarbons (molecules containing hydrogen and
carbon) and NO2 in the presence of sunlight (Graedel and
Crutzen, 1997). A large percentage of these hydrocarbons
come from vehicle emissions. Even though vehicles are
now checked annually for smog emissions, there has been
little change in the number of days each year with moderate or unhealthy amounts of O3. During the 1990s there
was an average of 80 days per year with O3 amounts rated
as moderate or unhealthy. This lack of improvement may
be because the increased number of vehicles during the last
decade has offset the gains realized from emission testing.
Particulate matter can be a problem in the areas in the
lee of the Sierra Nevada. The large areas of sparse vegetation can provide plenty of dust and sand that can be suspended in the atmosphere. Even relatively small particles
can decrease visibilities. Smoke, especially during the fire
season, can also contribute substantial amounts of particulate matter. Smoke from wood-burning stoves is not as
much of a problem now since their use has been restricted.
The number of days per year that had moderate amounts of
larger particulate matter (less than 10 microns) had decreased from around 50 per year in the early 1990s to
around 10 days per year in 1998 and 1999. The number of
days with unhealthy levels of these larger particulates has
decreased from two to four per year to zero.
Nitrogen dioxide is produced by automobiles and by
industrial sources. The Washoe County AQMD continuously monitors two industrial sites in the Reno-Sparks area
for NO2 emissions. The Truckee Meadows does not have
as much of a problem with this pollutant as do many larger
industrial regions. The emergence of a high tech component to Reno’s economy, and the area’s history as a warehousing and distribution center, may help to keep nitrogen
dioxide levels relatively low in the future.
The Washoe County AQMD states that sulfur dioxide
and lead are not significant pollutants in the Truckee Meadows (Washoe County Air Quality Management Division,
2002). These substances are mainly produced by industrial
processes. With the lack of heavy industry in the region, the
levels of these pollutants are fairly low. The AQMD still
monitors the levels of these substances, however.
The AQMD reports that there has been an overall
decline in pollutants such as carbon monoxide, ozone, and
particulate matter during the last ten years. This can be
attributed, at least in part, to many successful AQMD
initiatives such as the use of oxygenated fuels in the winter
months, the vapor recovery program for gasoline dispensing facilities, restrictions on residential wood burning,
Federal emissions limitations on new cars, and vehicle
inspections and maintenance requirements (“smog check”)
(Washoe County Air Quality Management Division, 2002).
The natural beauty that we see across our region should
give us an incentive to make the air even cleaner. This will
help to improve our already high quality of life.
GROWING SEASON AND FROST
Agriculture is a major part of Nevada’s economy. Although much of this industry is devoted to raising livestock, crop growing is also important. Because of the dry
climate, most of Nevada’s farmland is irrigated. And this
farmland is usually located in valleys. Hay, such as grass
and alfalfa, is grown as cattle feed. Wheat, barley, oats,
rye, and potatoes are some of the major crops that are
grown throughout western Nevada. The Carson, Walker,
and Truckee valleys contain much of the farmland. The
Lake Tahoe basin is mostly forested and does not have
nearly the percentage of farmland that western Nevada has.
One of the reasons that the Tahoe basin does not have
as many crops under cultivation is because of its relatively
short growing season. The growing season is often defined
as the average period of time between the last frost in the
spring and the first frost in the fall. This can also be defined as the frost-free season (Trewartha and Horn, 1980).
The growing season can also be defined as the length of
time between the last occurrence of a certain temperature
in the spring, and its first occurrence the following fall
(Sakamoto and Gifford, 1970).
Frost occurs when the temperature cools to the dew point
and the dew point is at freezing or below. Water vapor sublimates directly out of the atmosphere and is deposited on cold
surfaces as ice crystals. Air trapped in the ice crystals give the
frost a whitish appearance. Frost that occurs for only a few
hours at night may not be a big problem for agricultural interests. However, frost that occurs for much of the night can
adversely affect plants. A killing frost can be defined as a frost
period that “is sufficiently severe to end the growing season
(or delay its beginning).” (Glickman, 2000).
From the climatological record (for the period 1888–
1950) compiled by the U.S. Weather Bureau, the average
date of the last killing frost in the spring in Reno was May
14. The average date of the first killing frost in autumn in
Reno was October 6. The growing season in western Nevada can be shortened by a month or more by a late spring
or early autumn frost. At Reno (for the period 1888–1950)
the latest killing frost in the spring occurred on June 25,
1943, and the earliest killing frost in the autumn occurred
on September 6, 1900.
These dates have not changed appreciably during the
last 100 years. Based on frost/freeze data from the period
1951–1980 (USDC, 1988), the average date of the last
killing frost (temperature of 28°F or lower) at Reno occurs
on May 12. The average date of the first killing frost occurs
on September 30. At Carson City the average date of the
last killing frost of the season occurs on May 11, and (like
Reno) the average date of the first killing frost of the fall is
September 30. At Tahoe City the date of the last killing
frost in the spring is May 28. However, the relatively warm
water of Lake Tahoe may extend the growing season a bit.
The average date of the first killing frost in the fall at
Tahoe City is October 2.
The frost-free season lasts 120 to 130 days in valley
locations in western Nevada. It can be significantly shorter
at mountain locations with frost-free seasons of only
21
around three months in the upper elevations of the Lake
Tahoe basin. In a study of frost-free periods at Reno extending from 1906 through spring 2006, it was found that
the frost-free seasons have been getting longer during the
past couple of decades. From 1990 through the spring of
2006 the date of the last 32°F temperature in the spring at
Reno has been in April during nine of those seventeen
years. The date of the first 32°F temperature in the autumn
from 1990 through 2005 was in October during fourteen of
those sixteen years. In fact, the first occurrence of a 32°F
temperature in autumn 1992 was on November 3. This is
the only time during the period 1906 through 2005 that the
first freezing temperature in the autumn at Reno occurred
in November (O’Hara, 2006).
Still another way in which to define the growing
season is through use of an index called “growing degree
days.” The derivation of growing degree days (GDDs) is
similar to that used to derive cooling degree days (CDDs)
and heating degree days (HDDs). As mentioned in a previous section, both CDDs and HDDs use a base of 65°F in
order to determine the need for air conditioning or heating
in buildings. Growing degree days can be derived using
any of a number of bases. Common base temperatures that
are used are 40°F, 50°F, and (86–50°F). Each of these
bases is discussed below.
Photo by Larry Garside
Sakamoto and others (1977) defined a growing degree
day as a “unit based on the difference between a selected
base temperature and the mean daily temperature.” The
mean daily temperature is computed by adding the high
and low temperature recorded for a calendar day, then
dividing that sum by 2. For example, if the high temperature on a certain day was 72°F and the morning low was
36°F, then the average (mean) temperature for that day
would be 54°F (72 + 36 =108, 108 divided by 2 = 54). By
using a temperature base of 40°F there would be 14 GDDs
for this day (54 - 40 = 14). If 50°F was used as the base,
then there would only be four GDDs.
Growing degree days can be used for many purposes.
Sakamoto and others (1977) point out that vegetable canning companies can determine the number of GDDs that
are needed for maturation of various vegetables. This can
be more accurate than using a set number of calendar days.
As mentioned in Sakamoto and others (1977), “[i]t is
common knowledge that a cooler than normal spring or
hotter than normal summer slows plant growth. Therefore,
number of days to maturity based solely on calendar dates
can be misleading” [italics theirs]. Another use of GDDs
that they refer to is in the determination of the best times
during which to apply pesticides.
The University of Nevada Quadrangle and the Mackay Mines Building, January 22, 1997.
22
Photo by Mark Vollmer
Rain showers during a summer storm as seen from the Tahoe Rim Trail about 9000 feet above sea level.
Precipitation
by Brian F. O’Hara and Tom Cylke
RAIN
rain shadow effect can be clearly seen as Reno and Carson
City, in the valleys east of the Carson Range, receive less
than a third of the precipitation that falls at Tahoe City,
which is at a higher elevation in the Lake Tahoe basin
between the Sierra Nevada and the Carson Range (Figure
12). Figure 13 on page 10 shows the average annual
precipitation received across the eastern Sierra and western
Nevada.
Rainfall can occur across the region at any time of the
year . Even during the winter, when a strong storm may be
bringing heavy snowfall to the Sierra Nevada just west of
Reno, rain may be falling in the Truckee Meadows. It is
even possible for nothing to fall at Reno during significant
winter storms. Moisture-laden air associated with the
winter storm may deposit large amounts of snow on the
western slopes and summits of the Sierra in California.
The climate of western Nevada is one of the driest in the
entire United States. Table 3 and Figure 11 show average
monthly precipitation at Reno, Carson City, and Tahoe
City. Reno averages only 7.48 inches of precipitation for
the entire year, and Carson City receives slightly more at
10.36 inches. As in many parts of the western United States
(west of the Rocky Mountains) western Nevada experiences a biannual precipitation pattern (Trewartha, 1981).
Two-thirds of the precipitation falls as snow and rain
during the colder half of the year. There is a secondary
maximum during late spring when just around an inch of
precipitation falls during May and June at both Reno and
Carson City. It is clear that two-thirds of Tahoe City’s
32.66 inches of precipitation is also received during the
colder half of the year from November through April. The
Table 3. Average monthly and annual precipitation (inches) at Reno and Carson City, Nevada, and Tahoe City,
California (1971-2000).
Jan
Feb
Mar
Apr
May
June
July
Aug
Sep
Oct
Nov
Dec
Total
Reno
1.06
1.06
0.86
0.35
0.62
0.47
0.24
0.27
0.45
0.42
0.80
0.88
7.48
Carson City
1.82
1.66
1.26
0.42
0.52
0.40
0.22
0.32
0.51
0.69
1.26
1.28
10.36
Tahoe City
6.01
5.71
4.57
1.82
1.21
0.77
0.33
0.46
0.90
1.95
4.25
4.68
32.66
23
low pressure system forms at the surface.
The subsiding air in this upper-level high
pressure region suppresses the formation of
clouds, and the clouds that do form tend to
have high bases. Much of the rain that falls
from these high-based clouds evaporates
before it reaches the ground.
As the high pressure area strengthens
over Nevada during the summer the easterly
winds south of the high pull moisture in
from the Gulf of Mexico (and to a lesser
extent from the Pacific Ocean and Gulf of
California). This monsoonal moisture
contributes to increased thunderstorm
activity over the region. However, daytime
temperatures are typically at their highest
during July and August so, even with more
rain showers and thunderstorms occurring,
Figure 11. Average monthly precipitation (inches) at Reno and Carson
cloud bases tend to be at their highest so
City, Nevada, and Tahoe City, California (1971–2000).
rainfall has even less of a chance of reaching
the ground. This can explain why only ¼
However, most of the moisture may be wrung out of the air
inch of rainfall is normally recorded at Reno and Carson
mass before it reaches the valleys of Nevada east of the
City during either July or August, the two driest months of
the year.
Sierra. The downward motion of the westerly winds
Very little rainfall occurs during the warmer half of the
coming off the Sierra crest causes the air to compress and
year (May through October) in the eastern Sierra and
become warmer. This makes it less likely that clouds will
western Nevada. However, during intense thunderstorms,
form, making the probability of precipitation even less.
heavy rainfall can occur in a short period of time. The
However, during the winter, storm tracks are often
rainfall can also be extremely isolated. For example, on
located across Nevada. As these winter storms move across
June 21, 2002 only 0.10 inch of rainfall was reported at the
the region the chance of precipitation occurring in the Reno
official observation site at the Reno-Tahoe International
area is the greatest. Three or four winter storms may move
Airport. However, that evening, it was estimated that 2
across the region during just one month. The Reno area
inches of rain fell between 6:20 and 7:20 pm in the Spanish
may receive precipitation from each of these storms.
Springs area northeast of Reno. As reported in Storm Data,
During the summer the weather pattern changes. High
damage at the new Spanish Springs High School was
pressure moves north, which in turn pushes the storm
estimated at over one-half million dollars (USDC, 2002).
tracks to the north. Thus, western Nevada is not as much
under the influence of persistent storms as it is during the
Heavy precipitation of over one inch during a 24-hour
winter. Snowfall can occur even into May (and very rarely
period can be expected about once every year in western
has been reported at Reno in June), but precipitation during
Nevada. But these periods of heavy precipitation almost
the warm half of the year (mid April to mid October)
always occur during the colder half of the year (November
occurs mainly as rain.
through April). Tahoe City receives three to four times the
High pressure forms aloft over the Great Basin during
amount of precipitation that Reno and Carson City receive.
the summer and, due to heating of the ground, a thermal
This also is mainly from winter precipitation.
Figure 12. Diagram showing rain shadow effect. Moisture in air mass is deposited as precipitation on windward
side of barrier, leaving very little moisture to make it to leeward side.
24
Photo by Kris Ann Pizarro
Stratocumulus clouds in foreground and snow on Carson Range, looking northwest from Washoe Valley.
From 1906 through 2006, an inch or more of precipitation has been recorded at Reno on 54 days (O’Hara, 2006).
On 13 of those dates precipitation totals of 1.50 inches or
greater were reported. Some of the precipitation totals
resulted from only rain. This is especially true during the
warmer half of the year. However, during the winter, over
an inch-and-a-half of precipitation can be recorded on a
particular date, but some (or all) of it may be from snow.
By contrast, since July 1, 1948, Carson City has recorded
at least 1.50 inches of precipitation on 30 dates (mainly
during the winter months). These data reflect the generally
nighttime preponderance of precipitation during the colder
half of the year.
It should be noted that because Reno is an official
National Weather Service (and earlier Weather Bureau)
observation site, precipitation is measured once a day at
midnight. However, at cooperative observation sites
(staffed through the decades by volunteer cooperative
weather observers), precipitation is not measured at
midnight, but at other times. In the 1950s precipitation at
Carson City was measured at 6 am local standard time
(LST). In 2006 it was being measured at 5 pm LST. Thus
daily amounts at locations with similar climates (such as
Reno and Carson City) may show very different totals for
the same date.
This difference is clearly seen in the precipitation data
for Reno and Carson City. The eastern Sierra and western
Nevada experience a precipitation maximum at night
during the colder half of the year (November through
April) (Landin and Bosart, 1989). As a result, Carson
City’s weather observations, which have been recorded at
times other than midnight (usually in the morning or
evening), would account for an entire nightly precipitation
event. Reno’s daily precipitation observation, however, is
always recorded at midnight (for the calendar day). Thus,
an overnight precipitation event would be divided and
recorded on two separate dates (before and after midnight)
at Reno. This may be why Carson City has recorded so
many more daily precipitation events of over 1.00 inch
than Reno has.
When Reno’s data are looked at in a timeframe that
matches Carson City’s, both locations show similar totals
(but with Carson City slightly ahead in average annual
precipitation). With this diurnal nighttime maximum it
would seem that Carson City’s precipitation data may give a
better representation of the actual storm totals that are
received in western Nevada. This difference in observation
times should be kept in mind when comparing the precipitation data. Weather observers at Tahoe City, a cooperative
weather observation site with a long history, have also
measured precipitation at various times (in 2006 the daily
weather observation was taken in the morning at 8 am LST).
SNOW
Snowfall is common across western Nevada during the
winter. Snowfall amounts can vary widely both during a
winter storm and throughout the entire winter (Figure 13
on page 10). Locations in the eastern Sierra Nevada can
receive 2 or 3 feet of snow during a 24- to 48-hour period
while the same winter storm may only drop a few inches in
Reno or Carson City. At valley locations in western Nevada
snow cover usually does not last very long, often completely melting within a few days. On an annual scale,
snow cover throughout the winter can accumulate significantly in the Tahoe region with amounts measured in tens
of feet by early spring. Figure 14 compares the snowfall
and deepest snow depths recorded each winter at Reno and
at the Central Sierra Snow Laboratory at Soda Springs,
California, near Donner Summit. This location receives
huge amounts of snow from powerful snowstorms coming
in off of the Pacific. Reno, which is located in the lee of the
Sierra Nevada and the Carson Range, receives only a
fraction of the amount recorded near Donner Summit. This
is because most of the moisture associated with a snowstorm oftentimes is wrung out of the air mass as it ascends
the west slope of the Sierra Nevada. This moisture falls as
snow (and as rain in the lower elevations) west of the
Sierra crest with very little left over to be transported to the
valleys east of the range.
25
Figure 14. Total snowfall and maximum snowpack depth at the Central Sierra Snow Laboratory near Soda
Springs, California (1879–2003), and at Reno Nevada (1900–1995). Water years run from October through the
following September. For example, Water Year 1900 is from October 1, 1899 to September 30, 1900.
26
Figure 15 and Table 4 show the average
monthly snowfall reported at Reno, Carson
City, and Tahoe City. The rain shadow effect
mentioned above is even more pronounced in
the snowfall data than it was in the precipitation data (which includes rainfall along with
melted snowfall). Tahoe City receives over
eight times the snowfall amounts recorded at
either Reno or Carson City (Table 4).
Snowfall has not been recorded at Reno
during July and August and only a few times
during June. No snowfall has been recorded at
Carson City during these three months.
However, at Tahoe City, snow is sometimes
reported as late as June. Average annual
snowfall at Reno and Carson City is almost 2
feet, almost all of it occurring between mid
November and the end of March.
Figure 15. Average monthly snowfall (inches) at Reno and Carson
City, Nevada, and Tahoe City, California (1971–2000).
Lake Effect Snow
Western Nevada and northeastern California can occasionally experience lake effect snow under the right conditions, although not to the extent that areas in the lee of the
Great Lakes do. Two of the necessary ingredients for lake
effect snow are a cold air mass moving over a region and a
relatively warm water surface. These conditions can be
satisfied during the late fall and early winter as cold polar
air masses invade the region. Three of the largest lakes in
the area (Lake Tahoe, Pyramid Lake, and Walker Lake)
can generate lake effect snow as cold air passes over them.
In the fall, Pyramid Lake and Walker Lake can still be
relatively warm, although due to their relatively shallow
depth they cool down fairly rapidly as the winter progresses. Lake Tahoe, being over 1500 feet deep over much
of its extent, does not cool down as rapidly. The difference
in temperature between the relatively warm water surface
of Lake Tahoe and a cold air mass moving across it can
provide the instability necessary to promote the formation
of clouds and snowfall downwind of the lake.
Lake Tahoe, Pyramid Lake, and Walker Lake are
much smaller than the Great Lakes. For lake effect snowfall to be generated by these lakes, the air moving across
them must have a trajectory that will pick up as much
moisture as possible from the lake surface. This can happen
when the wind flow is out of the northwest when it crosses
Pyramid Lake. This takes the cold air along the long axis of
the lake bringing the air and warmer water surface in
contact with each other for the longest period possible. If
the wind is out of the west or southwest the residence time
of the air may not be long enough to generate many clouds,
let alone snowfall downwind of the lake. Walker Lake, the
smallest of the three lakes, is about 20 miles long along its
north-south axis but less than 10 miles wide at its widest
point. Like Pyramid Lake, lake effect snow is more likely
downwind of Walker Lake when the wind flow is from the
north or south along its longest axis.
Lake Tahoe is 22 miles long in its north-south axis
and 12 miles wide in its east-west axis. This is slightly
larger than the northern part of Pyramid Lake. However,
the topography around Lake Tahoe is much steeper than
that around either Pyramid Lake or Walker Lake. The
mountains around Lake Tahoe can combine with the
relatively warm lake surface to produce impressive bands
of lake effect snow downwind of the lake.
Washoe Valley can be impacted if the wind is out of
the west. The air moving over Lake Tahoe picks up
moisture, the mountains to the east help to intensify the
snowfall that is generated, and the snow is then carried
eastward and deposited not only on the Carson Range but
on Carson City and the surrounding areas as well. When
added to snow from a previous snowstorm the snow cover
can accumulate to impressive amounts. A half of a foot of
snow can fall within a few hours from a lake effect snow
event. An impressive lake effect snow event occurred in
early November 2000 when 23 inches of snow generated
by Lake Tahoe fell across the Carson City area (Cairns and
others, 2001). Due to the small scale of many of these lake
effect snow events, radar remains one of the best methods
of tracking and forecasting their extent (Huggins and
others, 2001).
Table 4. Average monthly and annual snowfall (inches) at Reno and Carson City, Nevada, and Tahoe City,
California (1971–2000).
Jan
Feb
Mar
Apr
May
June
July
Aug
Sep
Oct
Nov
Dec
Total
Reno
5.2
5.4
3.3
0.9
0.7
Trace
0.0
0.0
0.1
0.5
3.1
4.3
23.5
Carson City
6.3
4.0
3.2
1.1
0.5
0.0
0.0
0.0
0.1
0.2
1.2
4.6
21.0
Tahoe City
42.7
37.6
34.7
16.0
3.7
0.2
0.0
0.0
0.3
2.3
16.2
35.3
188.9
27
Photo by John James
Snow in the Sierra. Deep snow cover at Meyers, California during April 1969.
Historic Snowstorms
January 10–14, 1911. This was the greatest snowfall in
Reno from a single snowstorm since 1890. A total of 37.9
inches of snow fell from the 10th to the 14th. The 19.7
inches falling on the 12th is still the second greatest 24-hour
amount to ever fall in Reno. Trains and street cars were
unable to operate for 2 weeks following this storm.
Photo by Jennifer Mauldin
January 17–18, 1916. A record 22.5 inches of snow fell on
January 17 in Reno, with a 25.5 inch storm total by the
18th. This was the biggest of several storms during the
month that led to an all-time monthly record in Reno of
65.7 inches of snowfall. Figure 16 shows the area of low
pressure over the California coast on the morning of
January 17. This low moved through the Sierra and western
Nevada, and deposited the huge amounts of snow that were
reported. The 199 inches of snow measured at Marlette
Lake in the Carson Range east of Lake Tahoe set an alltime monthly record for the state of Nevada. Temperatures
dropped to a record -17° in Reno on the 21st following this
snow storm.
December 1–5, 1919. Five consecutive days of snowfall
totaled 33.6 inches for the biggest single December storm
in Reno’s history. Cold temperatures kept snow on the
ground until the 27th.
February 9-11, 1922. A total of 27.4 inches of snow fell in
Reno during this 3-day period. Even more fell in the Sierra
with 78.0 inches being reported at Tahoe City. Snow and
avalanches in the Sierra halted rail traffic at Reno until the 14th.
Snowfall in north Carson City as a result of a lake effect
snowstorm from Lake Tahoe during the winter of 2000–
2001. The actual depth of the lake effect snowfall from
this storm can be seen from the snow on the roof.
January 10–17, 1952. This snowstorm recorded 11.8 feet
of snow at Donner Summit over the 8-day period. On
January 13th the Southern Pacific luxury streamliner City of
28
Monday, January 17, 1916
Figure 16. Surface weather maps for January 17, 1916, 8:00 am EST; January 12, 1952, 1:30 am EST; and December
25, 1971, 7:00 am EST (pressure in millibars reduced to sea level). Maps courtesy of the NOAA Central Library Data
Imaging Project.
29
falling at Carson City. However, larger amounts were
measured in the Sierra with 44.0 inches of snowfall at
Tahoe City from the 25th through the 30th. Close to 5
feet of snow fell at Truckee during these dates.
Photo courtesy of the Nevada Historical Society
December 21–28, 1971. This Christmas storm
dropped 25.6 inches of snow in Reno over 8 days, and
the 14.9 inches on the 25th is the sixth largest 24-hour
amount since 1890. The cold front that moved
through the region on December 25 (Figure 16)
brought in an arctic air mass. The very cold temperatures that followed this storm lasted into early
January, and helped to keep several inches of snow on
the ground until January 19.
January 4-5, 1982. This storm set a Nevada 24-hour
snowfall record of 48 inches at Daggett Pass on the
southeast side of Lake Tahoe. During this two-day
period 29.0 inches of snow fell at Tahoe City. At
Carson City 13.0 inches of snow was reported.
Milder temperatures brought a mixture of rain and snow
to Reno during this period with 3.8 inches of snow
falling there on the 5th.
Snow cover in Reno in the winter of 1915–16.
San Francisco was trapped by a snow slide on Donner
Summit. As a result, 226 passengers were stranded for
three days until they were allowed to walk a half mile to
the newly plowed Highway 40. This was “the first time
since the exceptionally snowy season of 1892 that the
tracks of the Southern Pacific Company through Donner
Pass had been blocked for any considerable period” (Ludlum, 1952). Figure 16 shows the cold front
that moved through the Sierra Nevada on January 12.
This cold front helped in depositing the huge amounts of
snow reported across the region.
Almost 14 inches of snow fell in Reno, and up to 3
feet fell in outlying areas. Fifty-five mph winds blew
drifts up to 15 feet high in Washoe Valley and north of
Reno, stranding many vehicles
north and south of Reno. The
Mount Rose highway was closed
for six weeks, and Donner Summit
was impassable to auto traffic.
Skiers were stranded and had to be
rescued at the Mount Rose and Sky
Tavern ski areas. The only way in
and out of Reno was east to Fallon
which reported surprisingly little
snow.
November 8–12, 1985. A total of 16.3 inches of snow
fell in Reno over this 5-day period. The 15.2 inches of
snow that fell in Reno on the 10th set a November 24hour snowfall record. It is also the fifth largest one-day
snowfall total recorded in Reno since 1890. Snow
remained on the ground until Thanksgiving.
February 13–18, 1990. Snowfall from this 6-day storm
totaled 21.5 inches in Reno. Eighteen inches of this total
was measured on the 16th, setting a 24-hour record for
February, and going down as the third largest single day
January 24-30, 1969. Over a threeday period from January 24 to 26, a
total of 10.4 inches of snow fell in
Reno, with 11.0 inches of snow
Photo by Kris Ann Pizarro
February 7-12, 1959. This six-day
storm dropped 22.1 inches of snow
in Reno. The total of 13.2 inches
that fell on the 10th is the ninth
largest 24-hour snow amount ever
recorded in Reno. During this same
six-day period 16.9 inches of snow
fell at Carson City, with 44.0 inches
reported at Tahoe City.
Snow cover in Reno in February 1990.
30
snowfall amount at Reno since 1890. Figure 17 shows
the weather map for February 16. The cold front over
northeastern California moved through the Sierra and
western Nevada during the day.
December 30, 2004–January 1, 2005. This was the
first of two major snowstorms in as many weeks to
affect the region. This first storm dropped nearly 2 feet
of snow on the Reno and Carson City areas. Over 5 feet
of snow fell in the higher elevations of the Sierra. On
December 30 it was estimated that 16.4 inches of snow
fell in Reno, with an additional 4.9 inches falling on the
31st and another 0.6 inches falling on January 1. The
snowfall had to be estimated because the cooperative
weather observers, due to the impassable roads, could
not make it into Reno to make measurements. The
National Weather Service and the Western Regional
Climate Center estimated the snowfall from daily
precipitation received at the Reno airport, and from
snowfall, precipitation, and snow density measurements recorded at other locations across the RenoCarson City area. The 16.4 inches of snowfall that was
estimated for the 30th would make that the fourth
largest daily snowfall amount reported in Reno in the
last 100 years. The weather map for December 30 in
Figure 17 shows the cold front which moved through
the region and deposited the near-record snowfall
amounts.
A second snowstorm dropped another 16.4 inches
on Reno on January 7 and 8. By January 8, 20 inches of
snow cover was reported in Reno. As a result of the two
storms a total of 79 inches of snowfall was reported at
the National Weather Service Forecast Office in the
foothills north of Reno. Similar totals were reported in
the foothills west of Reno at elevations of around 5000
feet. Nearly two feet of snow cover paralyzed the
valleys of western Nevada for much of the month of
January. Up to 3 feet of snow cover was common in the
foothills west of Reno and Carson City. The snow depth
remained at least a foot in Reno through January 15 and
was not completely gone until February 1. Snowfall in
the Lake Tahoe basin above 8000 feet elevation totaled
10 to 15 feet from the two storms combined. The
snowfall and snow cover that resulted from these two
storms were the most seen in the region since the
incredible series of four snowstorms in January 1916.
Snow Cover
Figure 17. Surface weather maps for February 16, 1990,
7:00 am EST and December 30, 2004, 7:00 am EST (pressure
in millibars reduced to sea level). Maps courtesy of the
NOAA Central Library Data Imaging Project.
31
Even though the Reno and Carson City areas receive an
average of almost 2 feet of snow annually, snow
usually does not last on the ground very long. Due to
the mild daytime temperatures, and the generally sunny
skies during the winter months, snow cover usually
completely melts after just a few days. Snow depths
rarely exceed 6 inches because snowstorms in the Reno
area normally do not deposit this much snow. Large
amounts of snow can be deposited in the Sierra Nevada
Photo by John James
Snow cover at South Lake Tahoe during late winter, 1969. Homes were damaged from 15-foot
snowpack and 20-foot drifts.
Historic Winters
Winters are typically cold in western Nevada and the
Sierra Nevada, and snow can be expected, especially in
the Sierra, every winter. However, some winters are more
severe than others due to greater amounts of snow or
colder temperatures, or both. Listed below are some of the
winters that have stood out as being especially severe.
but by the time a storm system reaches the valleys east of
the Sierra Nevada most of the precipitation has been
wrung out of the air mass. Relatively little moisture is
left that can be deposited as snow (or rain) in the lee of
the mountains.
The higher elevations of the Sierra receive much
more snowfall than the drier valleys to the east. A total of
300 to 400 (or more) inches of snow can fall at some of
the ski resorts around the Lake Tahoe basin during a
typical winter. As this snow accumulates throughout the
winter its depth can reach ten feet by the middle of
March. This can be great for the ski slopes but it must be
cleared from streets and sidewalks. The deepest snow
cover ever recorded in the 48 contiguous United States
occurred at Tamarack, California (southwest of Lake
Tahoe) on March 9, 1911 when 454 inches (almost 38
feet!) of snow was measured (Wisler and Brater, 1959).
This was after receiving 390.0 inches of snow in January
1911 (a U.S. record) (Ludlum, 1982).
Deep snow cover does not prove to be an inconvenience very often for residents of the Truckee Meadows
and Eagle and Carson Valleys. However, there have been
some periods when snow cover has lasted for over a
month. And deep snow cover has sometimes lasted for
well over a week. Deep snow cover can be expected
every winter in the Tahoe Basin and residents there
prepare for it and are used to it. The deepest snow cover
reported at Tahoe City since 1931 was the 166 inches
that was on the ground on March 20, 1952.
1889–90. This turned out to be a record-breaking winter.
Temperatures were near normal through late autumn and
through most of December. A total of 5.7 inches of snow
was reported at Carson City on December 23 with
another 10.1 on the 24th and 4.9 inches on the 25th. A
strong cold front moved through the evening of the 28th.
After the front passed, the temperature dropped to -7° the
morning of the 29th. The temperature was still -1° at 1:30
that afternoon but finally rose to 15° that evening. The
total snowfall for December at Carson City was 31.4
inches.
The snowy pattern continued into January with
10.0 inches of snow falling at Carson City on the 3rd as
a cold front moved through. Very cold air settled over
the region. The low temperature on the morning of the
6th was -10º and it only got worse. The morning low
was -17° on the 7th and -22° on both the 8th and 9th.
There was even a report of the low at Carson City
reaching -27° on January 8. At Reno the temperature
bottomed out at -19° the morning of the 8th. This
remains the all-time record low at Reno. Snow returned
to the region in mid January and 20.1 inches fell at
32
Photo courtesy of the Nevada Historical Society
Carson City on the 17th. The total snowfall for the
month at Carson City was 55.1 inches. Warmer
weather in late January and early February helped
to melt much of the snow. Mild weather continued
through the first half of February. Then over a
period of four days (the 16th through the 19th) a
total of 22.7 inches of snow fell at Carson City. On
the 25th very strong winds blew the snow into
drifts, blocking the Virginia and Truckee Railroad
for two days. Total snowfall at Carson City during
February was 26.9 inches. On the morning of the
27th the temperature fell to -3º at Carson City.
The winter was severe across the entire state of
Nevada. Temperatures in January fell to -42º at
Elko and -39º at Beowawe. Farther south at Ely the
lowest temperature during January was -27° and at
Eureka the thermometer hit -26º. February was also
cold. The lowest temperatures recorded for the
month were -41º at Elko, -20º at Beowawe, -23º at
Ely, and -19º at Eureka. Across northern Nevada
the harsh weather took a toll on livestock on the
open range.
Commercial Row at Southern Pacific Railroad Depot in Reno
during the winter of 1915–16.
1915–16. The winter of 1915–16 started out as fairly mild.
Cold temperatures did not invade the region until the last
week of December. A snowstorm moved through the Sierra
the first week of January dropping 31.0 inches of snow on
Tahoe City on January 3. Temperatures stayed above zero
in western Nevada until the second week of January when
a snowstorm moved through the region dropping 13.8
inches of snow on Reno. On the morning of the 11th a low
of -1º was reported at Reno. The temperature fell to -9° the
following morning. At Tahoe City the temperature dropped
to -14° on the morning of the 11th and -8º on the 12th. A
week later an even bigger snowstorm dumped 22.5 inches
of snow at Reno on January 17 and another 3.0 inches on
the 18th. The 22.5 inches of snow that fell on January 17
remains the all-time largest single day total for Reno.
Travel was at a standstill. Railroad passengers were
stranded at Reno, Carson City, and other locations
because trains could not make it through. Temperatures at
Reno fell to -11° on the 20th and -17° on the 21st. Still
another snowstorm later in the month dropped 14.7 inches
of snow on Reno over a three-day period (27th through the
29th). The thermometer plummeted again with lows of -4°
and -13° being reported at Reno on the 30th and 31st,
respectively. At Tahoe City the temperature dropped to 15° on the 30th and it was -14° the morning of the 31st.
The 65.7 inches of snow that fell at Reno during January
1916 is still the all-time record monthly total for the city.
Record snow cover during January made travel nearly
impossible. After the snowstorm, during the second week of
January over a foot of snow was on the ground at Reno. As a
result of the 22.5 inches of snow that fell on the 17th, a record
30 inches of snow depth was reported in Reno. The snow
depth did not drop below 10 inches for more than a week.
The big snowstorm during the last week of the month
brought the snow depth back up to a foot and a half. February was relatively mild and the warmer temperatures caused
most of the snow at Reno to melt by the middle of the month.
1936–37. Conditions were fairly mild until late December when a total of 14.2 inches of snow fell at Reno
from the 27th through the 31st. A second snowstorm
during the first week of January brought much colder
temperatures. The low temperature dropped to zero at
Reno on the 6th. The temperature dropped to below zero
on each of the next seven mornings. The low on the
morning of the 8th was -16º and the low on the 9th was 14º. Snow cover of nearly a foot helped to keep conditions cold across western Nevada. At Tahoe City it was
-9º on the mornings of January 7 and 8th, and -14º on
the 9th.
A cold front in mid January did not bring much
snow but it reinforced the cold temperatures. At Reno
the morning lows were -12° on the 20th and -14° on the
21st. It was also cold at Tahoe City where the temperature dropped to -13° on the 20th and -14° on the 21st. The
coldest temperature reported in the region was at Boca,
California (in eastern Nevada County northeast of
Truckee). On the morning of the 20th the temperature
dropped to an incredible -45°! This remains the all-time
record coldest temperature for the entire state of California.
A significant snowstorm in late January brought 17.0
inches of snow to Reno over a three-day period (28th
through the 30th). Nineteen inches of snow covered the
ground at Reno on January 30. However, as in the severe
winter of 1915–16, mild weather in February helped to
melt the snow in the valleys of western Nevada so that
most of it was gone by the middle of the month.
1948–49. Cold temperatures were the main problem during
the winter of 1948–49 in a region stretching from the
western Great Basin to the Rockies. January 1949 ranks as
the coldest January on record in Reno. December 1948 is
the sixth coldest December on record in Reno, and February 1949 is the eighth coldest February ever. December
1948 was not especially snowy in the valleys east of the
33
Reno were still cold for late March. On the 20th, 21st, and
22nd the temperature dropped to 6º, 1º, and 5º, respectively,
still all-time record lows for those dates in Reno. On those
same dates at Carson City, the morning lows were 4º, -5º,
and -2º, also record lows for those dates. It was -5º at
Tahoe City on the morning of the 20th.
Sierra. The largest daily snow amount at Reno was 3.5
inches that fell on December 26. However, at Tahoe City,
36.0 inches of snow fell on December 14. A cold air mass
settled over the region and morning lows in late December
were barely above zero.
The very cold weather continued through January; 21
of the 31 days had morning lows below zero at Reno. Two
snowstorms, one in early January and one in mid January
deposited only around 5 inches of snow each, but the very
cold temperatures kept this snow on the ground through
January and the first half of February. At Reno the morning
low was -16° on January 25 and -15° the next day. These
remain some of the coldest days on record in Reno. Five
days in February also had lows below zero at Reno. In
Carson City the temperature dropped to -16º on January 25
and to -20º on the 26th. This -20º reading is the record low
temperature for January at Carson City (using official
weather data for Carson City starting on July 1, 1948).
The very cold conditions were also felt across much of
the rest of Nevada. Because of the deep snow cover over
much of northern and central Nevada, livestock on the
open range were stranded. Ranchers had difficulty getting
food to their livestock and 10 to 25 percent of the animals
died (Houghton and others, 1975). In what became known
as “Operation Haylift” hay was dropped from airplanes in
order to feed the isolated cattle.
1968–69. This was a snowy winter across the Sierra and
western Nevada. Three snowstorms in December dumped
almost ten inches (9.1 inches) of snow on Reno, with larger
amounts in the Sierra and Carson Range. The snowy
conditions continued into the next year. A snowstorm in
late January dropped 10.4 inches of snow on Reno. In the
Sierra (at Tahoe Meadows) 37 inches of water equivalent
fell as snow during the month of January (a record for
Nevada). February saw even more snow. The 23.5 inches
of snow that fell in Reno in February makes this the fourth
snowiest February in Reno’s history. Heavy snowfall also
occurred in the mountains. The Mt. Rose Highway was
closed for six weeks from late January to early March due
to the deep snow. On March 1 the snow depth at Tahoe
Meadows was 14 feet 7 inches (also a record for Nevada at
that time). The winter turned out to be near average in
temperature. In fact, relatively warm conditions in early
January helped Reno record an average temperature for the
month (37.0°) that was 6.6 degrees above normal.
1951–52. This was a very snowy winter in the Sierra
Nevada. A snowstorm in mid January made travel in the
Sierra impossible because roads and railways were blocked
by snow. In Reno 13.8 inches of snow fell from January 11
to 16. At Tahoe City 42.0 inches fell on the 15th alone.
Average daily temperatures at Reno were more than 10°
below normal from January 16-19 with low temperatures
of -2° on the 17th and -4° on the 19th. The snow was
especially deep at Lake Tahoe. Over 3 feet of snow (38
inches) was on the ground on December 7. It only
increased from there. By December 31, 78 inches of snow
cover was reported at Tahoe City (still a record snow depth
for that date). On January 12 there was 110 inches of snow
on the ground, and it increased to 120 inches (10 feet) by
January 17. February did not see many problems but snow
returned in March. Through most of February temperatures
were near normal and snow did not accumulate in the
valleys of western Nevada. The snow was deeper in the
Sierra; the snow depth at Tahoe City remained around 10
feet throughout February and into mid March. On March
14 a powerful snowstorm deposited 13.6 inches of snow at
Reno, and another 3.5 inches fell the next day. At Carson
City 14.5 inches fell on the 15th. The morning low at Reno
was 3° on the 16th and 9° on the 17th. These are still the
record lows in Reno for those March dates.
A total of 5.9 inches of snow fell on the 18th and 19th at
Reno, and on the 19th and 20th, 8.5 inches fell at Carson
City. At Tahoe City 28.0 inches fell on the 19th. The next
day (March 20) 166 inches (13.8 feet) of snow was on the
ground. This is the greatest snow depth ever recorded at
Tahoe City. The snow cover kept conditions cold. Even
though they did not drop below zero, the morning lows at
1992–93. An impressive period of deep snow cover
occurred from late December 1992 through all of January
1993. Even though the total period of time was just over a
month, on 20 of those days at least 5 inches of snow cover
was reported at Reno. And at least 10 inches of snow was
on the ground on 11 days at Reno. The period started with
an impressive snowstorm that dumped 12.9 inches of snow
on Reno from December 28 to 30. At Carson City 17.0
inches of snow fell on the 29th and 30th. At Tahoe City, 76
inches of snow was on the ground on January 1.
A series of storms through the first half of January
continued to add to the snow cover, and cold weather kept
the snow from melting. The temperature at Reno dropped
to -3º the morning of January 3rd and -1º the next day.
A low of -1º was reported again on January 12. At Carson
City the temperature dropped to -1º on the 11th and to an
impressive -14º on the morning of the 12th, record low
temperatures for those dates. A snowstorm the first week of
January dumped 8.1 inches of snow at Reno, and by
January 8, a total of 10 inches of snow was on the ground.
Except for two days (January 9 and 15), at least 10 inches
of snow cover was reported each day at Reno from January
8 through the 20. Warm weather late in the month finally
started to melt the deep snow cover.
2004–05. Autumn 2004 did not portend the incredible
winter that would unfold in December. A snowstorm on
November 27 dumped 7 inches of snow on Reno—not an
unusual occurrence. Cold air filtered into the region with
average temperatures 15 to 20° below normal in late
November and early December. Temperatures the rest of the
month were near normal but things were about to change.
34
Photo by Christine Mauldin
Snow cover in Carson City, winter of 1992–1993.
From December 30 through January 1, historic amounts
of snow fell on the region. Nearly 2 feet of snow fell in
Reno and Carson City. Three to 5 feet of snow fell in the
foothills of the Carson Range and 6 to 8 feet in the higher
elevations of the Sierra. A second snowstorm moved
through the region a week later, depositing almost as much
snow as the earlier storm did. The region was paralyzed by
this almost unprecedented series of snowstorms. The only
thing comparable was the series of four snowstorms that
moved through the region during January 1916.
Temperatures were below normal throughout the
month of January but not as cold as some other winters.
Average daily temperatures during the month were below
normal for all but five days at Reno. The deep snow cover
helped to keep temperatures low. The snow also contributed moisture to the lower atmosphere through evaporation
and melting during the day. The temperature inversion that
formed kept this moisture near the surface and dense fog
was reported through most of the last half of January and
into the first week of February. This dense fog, like the
heavy snowfall that preceded it, was almost unprecedented.
Dense fog was reported at Reno for nine consecutive days
in late January and for another five consecutive days in
early February. On only two other occasions in the last 60
years had dense fog been reported for nine consecutive
days or longer. In addition to the nearly unprecedented
snowfall and dense fog, an ice storm occurred on January
25—a relatively rare event for the Truckee Meadows.
The rest of the winter was near normal, which seemed
like a relief to many residents of the region. Both February and March had near normal temperatures and precipitation. But memories of the incredible pair of snowstorms
that visited the region in late December and early January
will probably remain with many residents for years to
come.
ICE STORMS
Ice storms are usually not a major problem in the RenoCarson City-Lake Tahoe region but they can occur, as was
experienced in late January 2005. Ice storms are more
prevalent farther to the northeast in places such as the
Winnemucca area. The publication Storm Data did not list
any significant ice storms in the Reno-Carson City-Lake
Tahoe area for the period 1959 through 2004 (USDC, 1959
-2005). For ice pellets (sleet) or freezing rain to occur at
the surface there has to be a layer of cold air (temperature
below freezing) at ground level with a layer that is warmer
than freezing above it. Snow that falls into the warm layer
melts into raindrops and these raindrops then freeze as they
pass through the cold layer of air at the surface. If the cold
layer is deep enough the raindrops will freeze into ice
pellets. If the cold layer is fairly shallow the raindrops will
not have time to freeze but will freeze when they come into
contact with structures, trees, and other vegetation that are
below freezing.
35
Photo by Heather Angeloff
Fog over the Truckee Meadows, looking southwest toward Mount Rose.
Humidity
by Brian F. O’Hara
Even though western Nevada has a dry climate, relative
humidity typically varies throughout the day. This diurnal
variation is mainly the result of changes in air temperature.
The relative humidity, however, can also respond to
changes in moisture in the lower atmosphere.
This process can be seen in the data for Reno in Figure
18. For any month throughout the year, the highest relative
humidity is recorded when the air temperature is at its
lowest, typically near sunrise. Similarly, the relative
humidity is at its lowest in the late afternoon or early
evening when the air temperature is at its highest. The
relative humidity is higher during the winter because the
amount of water vapor in the air does not vary as much as
the temperature does throughout the year.
The air mass over western Nevada is fairly dry throughout the year. Additionally, the air is quite warm during the
summer and cold during the winter. However, it is not correct
to say that the warmer air during the summer can hold much
more moisture than the cold air of winter can. Bohren and
Albrecht (1998) point out that a change in relative humidity
is the result of changes in evaporation and condensation, not
an air mass’s supposed ability to “hold” moisture.
When the air temperature is higher than the dew point
temperature there are more water molecules in the air mass
that are evaporating than are condensing. As an air mass
cools, its molecules have less energy (are less energetic) and
so, by moving more slowly, have a better chance to condense. When the air temperature equals the dew point
temperature there are approximately the same number of
water molecules evaporating as are condensing. Thus, since
the moisture does not vary much throughout the year over
the western Great Basin, the air is closer to saturation
during the winter than it is during the summer since the
wintertime temperature is closer to the dew point temperature. This is why the relative humidity is higher during the
winter than during the summer.
But a change in temperature is not the only thing that
can affect relative humidity. A change in the moisture
content of the air mass can also change the relative humidity. The Southwest Monsoon is a phenomenon that affects
relative humidity during the late summer over the Great
Basin. During the late summer, southerly winds from the
Gulf of California and Pacific Ocean (and even from the
Gulf of Mexico) transport moisture across Arizona and into
the Great Basin. This added moisture can contribute to
afternoon thunderstorm development, especially over the
eastern Great Basin (Whiteman, 2000). This thunderstorm
development can also extend into the western Great Basin.
Due to the monsoon, humidity values can also increase
(Figure 18). After reaching an annual minimum during the
day and night in July, the relative humidity starts to increase in August. Late summer temperatures can also be
affected. The additional cloud cover that results from the
monsoonal moisture and the afternoon thunderstorms in
late summer also helps to keep average temperatures lower
than those recorded during July.
FOG
Fog forms as a result of condensation exceeding evaporation in an air mass. Water vapor is added to the air either
from being evaporated from a water surface, or by being
advected (moved into a region by wind flow), thus making
the resident air mass more moist. When an air mass is
saturated, this means that condensation equals evaporation
at that temperature and pressure. If additional water vapor
is added to the air (either through evaporation or advection) then water molecules are forced out of the air and
they become suspended as fog droplets.
Visibility may be fairly good if the fog is just starting
to form. If additional water vapor molecules are not forced
into the air mass, then the fog may remain relatively light
36
Figure 18. Average daily variation in relative humidity at Reno, Nevada (1971–2000).
37
Photo courtesy of the Nevada Historical Society
Pogonip along the Truckee River (c. 1910).
with no decrease in visibility. However, if water vapor is
continually added to the air mass, or if the temperature of
the air continues to drop (or a combination of the two) then
fog can become denser. Visibilities can decrease rapidly if
moisture is added to the air mass quickly or if the temperature drops quickly. Dense (sometimes referred to as
“heavy”) fog is defined by the National Weather Service as
fog restricting visibility to ¼ mile or less.
Dense fog is not a significant hazard in Reno (Figure
19). Fog is mainly a wintertime phenomenon. During the
summer the air mass is usually very dry. Even as the
temperature drops at night the air mass does not get very
close to being saturated. In July the dew point may be 15º F.
The air temperature may be in the 90s during late afternoon and drop into the upper 50s at night. Since the
atmospheric moisture does not change appreciably, the
relative humidity stays low.
During the winter, the dew point may also be 15º F.
However, the air temperature may drop to 15º or less at
night. In this situation the air may become saturated. With
any additional cooling water vapor would condense out of
the air mass and fog could start to form. Snow cover could
contribute to the formation of fog as the snow on the
ground evaporates moisture into the relatively dry air mass
above it while simultaneously cooling the air. Dense fog
can form this way. In the valleys of western Nevada this
may happen, on average, on two or three days during both
December and January. Longer periods of dense fog
however, are relatively rare. This usually requires snow
cover in order to produce the evaporation that would cause
fog to form for many nights in a row. Since the winter of
1948–49 dense fog (restricting visibility to ¼ mile or less)
has formed for five or more consecutive days on only 10
occasions. Two of the periods of five or more consecutive
days of dense fog occurred after the two historic snowstorms that moved through the region in late December
2004 and early January 2005.
FREEZING FOG (POGONIP, RIME)
Fog mainly occurs during winter nights when the temperature drops to the dew point. Often the dew point will
be below freezing and the fog that forms under these
conditions is referred to as freezing fog. The accumulation of ice, or rime, which results from freezing fog, coats
plants or any other surface that is colder than freezing. In
Nevada, this rime is sometimes called pogonip. Houghton
and others (1975) stated that the term pogonip is thought
to come from the Paiute word “meaning ‘white death.’
The cold, damp conditions accompanying these fogs
made the people more susceptible to illness in the outdoor
environment.”
Figure 19. Average number of days with dense fog
(visibility ¼ mile or less) at Reno, Nevada (1943–2004).
38
Drought and Evaporation
by John W. James and Gary Barbato
DROUGHT
cant portion of the water that is used in this region. During
wet periods there is plenty of runoff to keep Lake Tahoe
high. During normal periods Lake Tahoe is not usually
below its rim (elevation: 6223.0 feet) but, during dry
periods, the surface of Lake Tahoe sometimes falls below
its natural rim. Thus, Lake Tahoe’s elevation can be a good
indicator of whether the region is suffering from a drought
or not. Figure 20 shows how the level of Lake Tahoe has
fluctuated throughout the twentieth century. The severe
droughts of the mid 1920s to mid 1930s, the mid 1980s to
mid 1990s, and the early 2000s can clearly be inferred
from the graph.
Nevada is typically dry, but we usually don’t consider
the lack of moisture a significant problem until we experience conditions that are abnormally dry, such as when the
water level in wells starts to drop, or the price that we pay
for water goes up (this is a concern that many people in the
eastern United States may never think about). Drought is
common in the region during the warmer half of the year
(April through September). However, midwinter droughts
have the most significant impacts on the region because of
the dependence on snowpack runoff from the Sierra
Nevada for water supplies.
Reno has an average annual precipitation of only 7½
inches, and only 50 rainy days per year (a rainy day is
defined as a day with at least 0.01 inches of rain). It is even
drier in Las Vegas, with an annual precipitation of only 4
Webster’s Dictionary defines drought as “a long spell of
dry weather.” If that definition is correct, then most of the
arid Southwest is usually in year-round drought. Perhaps a
more accurate definition is found in the Glossary of
Meteorology (Glickman, 2000), which defines drought as a
“period of abnormally dry weather sufficiently long
enough to cause a serious hydrological imbalance.” This
seems closer to what we think about when we talk about
drought. However, Landsberg (1982) stated that “[n]o
universal definition of drought exists, although there are a
number of localized definitions for various geographical
areas, usually geared to such aspects as crop yields,
reservoir levels, or stream flow.” For example: the wettest
water year in Reno was 1889–90 when 16.39 inches of
precipitation fell. If only 16.39 inches of precipitation fell
at Tahoe City, it would be the fourth driest water year on
record there (the driest water years on record were 1976–
77 (8.82 inches), 1986–87 (14.37 inches), and 1975–76
(15.58 inches)). (A water year is defined as the 12-month
period from October 1 to September 30 of the following
year. A water year is often designated by the year in which
it ends: for example, the 1977 water year extended from
October 1, 1976 through September 30, 1977.).
Reservoir (or lake) levels seem like a good measure of
the availability of moisture in the eastern Sierra and
western Nevada. The Lake Tahoe basin supplies a signifi-
Figure 20. Monthly surface elevation of Lake Tahoe (1900–2004).
39
strict conservation measures concerning the water balance
(precipitation/evaporation ratio), can lessen the problem.
Redmond (2003) stated that “in the Southwest the regional
water allocation and distribution system has not been tested
by a major drought within the residence time of a large
fraction of the current population.”
inches and 25 rainy days per year. In the Greater Reno and
Carson City area, with well over a half-million people,
water is supplied by rivers flowing down the eastern slopes
of the Sierra Nevada, and from deep wells.
Neither of these sources is sufficient during times of
drought. For example, in the spring of 2004, Lake Mead
dropped to its lowest level since the mid 1960s. Lake
Tahoe also responds to drought, as Figure 20 shows. Other,
smaller lakes, certainly respond to drought. The photos on
page 11 show Washoe Lake when it was nearly completely
dry in 2004 and when it had filled again in 2006. Dry
weather and population demands on water have greatly
increased in the past twenty years in western Nevada and
the Lake Tahoe region. Thus, such a definition of drought
as noted in the dictionary is not sufficient, and much
refinement is needed in order to fit regional differences.
Most of Nevada is semiarid, and periods of drought
only exacerbate the problem of lack of water (upper photo
on page 41). But drought can also affect the higher elevations (lower photo on page 41). Major droughts occur, on
average, around every 20 years. This is true for much of
the central and western U.S. (Landsberg, 1982). A drought
during the mid 1920s to mid 1930s was “possibly the most
severe and longest of this century” (Moosburner and
Williams, 1990). The droughts of the mid 1980s to mid
1990s, and the early 2000s, were also severe and, referring
to how rapidly the level of Lake Tahoe dropped, may turn
out to be even more severe than the 1920s–30s drought.
The driest water year on record in Reno was 2000-01, and
the driest two consecutive water years occurred in 1975-77.
Table 5 lists some of the most severe droughts in the RenoCarson City-Lake Tahoe area during the last 100 years.
In the past, there was nothing to lead to the conclusion
that water would be the ultimate growth control. However,
the tremendous and unexpected population growth in the
arid Southwest has put water availability in the center
spotlight for future planning. Education of the public, and
EVAPORATION
There is typically very little moisture in the lower atmosphere over western Nevada, and temperatures during the
day can be quite high. As a result, water can evaporate
from the surface of any area of standing water. This can be
especially pronounced over large lakes in the dry desert
areas of western Nevada. The rate of evaporation can be
determined by using instruments, the most common of
which is the evaporation pan. A Class-A evaporation pan
(which is one of the most commonly used in the western
United States) is about 4 feet in diameter and around 10
inches deep.
Evaporation can occur at a faster rate over the water
surface in an evaporation pan than it does over a large lake
(Sellers, 1965). Lake evaporation is very difficult to
measure directly. However, the rate from an evaporation
pan can be calibrated to give a good approximation of
evaporation from natural lakes and other bodies of water.
During the winter, evaporation from lakes in western
Nevada is negligible because the lake surface may be
frozen or the temperature of the water surface may not
exceed the dew point of the air above it. Because of this,
evaporation is not measured from pans during the winter.
However, from late spring through early fall the air
temperature is high enough to cause evaporation from
water surfaces. During a typical month in the summer only
a quarter of an inch of rain may reach the surface, but
during that same month a foot or more of water may
evaporate into the atmosphere from a large lake in the high
desert (Figure 21).
Of the dozen or so evaporation pans located across
western Nevada and the eastern Sierra two are in the RenoCarson City-Lake Tahoe region. Honey Lake, just across
Table 5. Average annual precipitation in inches during
drought (with percent of normal precipitation).
Years
Reno
Tahoe City
Central Sierra
Snow Lab
Average annual precipitation
1971–2000
7.48
32.66
64.68
Drought years (water years)
1924–35
6.29 (84%)
25.07 (77%)
37.58 (58%)
1946–49
4.95 (66%)
25.91 (79%)
45.13 (70%)
1976–79
5.91 (79%)
18.20 (58%)
46.44 (72%)
1987–94
5.77 (77%)
24.08 (74%)
50.37 (78%)
2001–04
5.21 (70%)
25.25 (77%)
51.57 (80%)
Figure 21. Average pan evaporation totals at Honey
Lake, California (1970–2004), and Lahontan Dam, Nevada
(1948–1974).
40
so evaporation rates from it are somewhat lower than those
at Lahontan Dam.
These large evaporation rates certainly contribute to
the water deficits seen across much of the western United
States. Often the moisture is not made up until winter when
large amounts of snow fall on mountainous regions. Even
the large snowpack that results still may not make up for
the water that was lost during the warmer months.
Photo by John James
the state line in California, is a station with one of the
longest evaporation records. Honey Lake Fleming Fish and
Game has been in operation for over 35 years. Pan evaporation at this location is right at 50 inches per year from
April through October. The other location is at Lahontan
Dam, between Reno and Fallon, Nevada. Pan evaporation
there averages 68.59 inches per year. It should be noted
that the pan at Honey Lake is in a partially irrigated area,
Photo by John James
Drought affects the Truckee River in downtown Reno, October 1991. Example of
conditions during the drought of the late 1980s and early 1990s.
Drought affects the upper Truckee River near Tahoe City in 1991. Example of conditions
during the drought of the late 1980s and early 1990s.
41
Photo by Chris Ross
Photo taken from Windy Hill in the late 1970s. Note the dust blowing across the eastern part of Truckee Meadows.
Wind
by Brian F. O’Hara
Wind is common over western Nevada as anyone who
lives in the region soon learns. Westerly winds over the
region are caused by the strong afternoon heating experienced over the Great Basin during the summer. This
heating causes pressure over western Nevada to be lower
than over the adjacent Sierra Nevada. A “thermal trough”
is thus formed over western Nevada. This difference in
pressure generates winds that descend the eastern slopes of
the Sierra (Hill, 1993). These winds are generally stronger
near the base of the Sierra and decrease in speed as they move
east through the Truckee Meadows and Washoe Valley.
The diagrams in Figure 22 show the percentage of
time the wind is from various directions for each month at
Reno. There is a definite westerly component to the wind
during the warm half of the year at Reno. This westerly
wind is a common occurrence during summer afternoons in
the valleys just east of the Sierra. Winds during the winter
are generally from the south. This is due to the strong high
pressure area that often forms over the Great Basin during
the winter. Winds can come from any direction as synoptic
-scale low pressure areas move through the region. Wind
gusts associated with thunderstorms can also come from
any direction.
There is also a definite diurnal (daily) pattern to the
wind. Figure 23 shows how the average wind speed
changes throughout the day for each month throughout the
year at Reno. During the winter the average afternoon wind
speed does not differ much from the wind speeds recorded
during the night. However, this changes during the late
spring and summer. Wind speeds generally decrease during
the night. But during the day, with the higher sun angle and
relatively drier atmosphere, the air near the surface quickly
warms during the morning and early afternoon. The rising
air motions that are generated induce a corresponding
increase in the horizontal winds at the surface. During the
warmer half of the year, wind speed increases very quickly
during the morning hours, and the wind is generally
stronger during summer afternoons than it typically is
during the winter (Figure 23).
It is worth noting that Reno has one of the lowest
average wind speeds in the nation (6.5 mph). Reno has a
perception as a windy place due to the fact that the winds
generally occur during the afternoon and evening hours,
especially during the summer.
WASHOE ZEPHYR
As mentioned above, due to the strong heating which occurs
over the Great Basin, winds during the summer tend to blow
from the west during the afternoon (Hill, 1993). Depending on
the strength of the high pressure area east of the region winds
can become quite strong. This afternoon westerly wind has
been dubbed the “Washoe Zephyr” and has probably been
observed as long as the region has been settled.
42
Figure 22. Average wind speed and direction by months at the Reno/Tahoe International Airport (1949–
2003). The lengths of the radial bars represent the percentage of time the wind blows from each of the 16
directions. The width and shade of each segment of the bars indicate the wind speed, and the length of the
segments indicates the percentage of time the wind blows at that speed from that direction.
43
Figure 22 continued.
44
Figure 23. Average daily variation in wind speed (miles per hour) at Reno, Nevada.
45
Figure 24. Formation process of mountain lee wave clouds.
MOUNTAIN LEE WAVES
A zephyr is a west wind (deriving its name from
Zephyros, the Greek god of the west wind). The Washoe
Zephyr descends the eastern slopes of the Carson Range
and is strongest as it moves through Washoe Valley. In his
book Roughing It, Mark Twain ([1872] 1995) described
this strong wind as it moved through Carson City:
Upper level winds are responsible for some of the most
interesting cloud patterns seen over the western United
States. One of these patterns is the mountain lee wave
cloud. As the name implies, these clouds are formed
downwind of large mountain ranges. The mountains
disrupt the upper level wind flow, causing the air to undulate in an up and down pattern. As the air moves higher in
the atmosphere it cools and its water vapor condenses into
a cloud. Downwind of the wave crest the air is moving
downward. This downward motion causes the air to compress and become warmer. As a result, the cloud evaporates. Even though the air is moving in a wavelike pattern
downwind of the mountain range the only part of the
pattern that is visible is the top of the wave where water
vapor has condensed into a cloud.
These waves do not move in relation to the mountains
that are causing them so the resulting clouds do not move
either (Wallington, 1966). These standing wave clouds, as
they are called, can take many shapes, but they often have
a lens shape with a rounded top and either a flat or a
concave base. These lens-shaped clouds, called lenticular
clouds, are common forms of mountain lee wave clouds.
As the air rises downwind of the wave cloud a second
wave cloud (or even a third or fourth) may form. A series
of lee wave clouds can extend for 100 miles downwind of a
large mountain range (Figure 24). Clouds may even form
just above the mountain itself, in which case it is called a
mountain wave (Scorer, 1972).
Due to the high elevation of the Sierra Nevada, mountain lee wave clouds are occasionally seen downwind of it
as shown in the cover photo and the photo on the next
page. Conditions can be turbulent near the clouds themselves. The turbulence can even extend to the lower atmosphere, and rotor clouds can sometimes be seen below a lee
But seriously a Washoe wind is by no means a
trifling matter. It blows flimsy houses down, lifts
shingle roofs occasionally, rolls up tin ones like
sheet music, now and then blows a stage-coach
over and spills the passengers; and tradition says
the reason there are so many bald people there, is,
that the wind blows the hair off their heads while
they are looking skyward after their hats. Carson
streets seldom look inactive on summer afternoons,
because there are so many citizens skipping around
their escaping hats, like chambermaids trying to
head off a spider.
Mark Twain, Roughing It
In a study conducted during July and August 1998,
Kingsmill (2000) found that the “valley stations all show a
clear diurnal wind pattern in association with the Washoe
Zephyr.” He found that at sites in Washoe Valley and
around Carson City in Eagle Valley wind speed increased
during late morning, but that the Washoe Zephyr started 2
to 4 hours later on sites to the north in the Truckee Meadows (Kingsmill, 2000). The Washoe Zephyr lasted longer
in the Washoe Valley, ending 1 to 2 hours later than it
ended in the Truckee Meadows. Another difference that
Kingsmill found is that the Washoe Zephyr kept a generally westerly component in the Truckee Meadows but it
came from a more southwesterly direction while in the
Washoe, Eagle, and Carson Valleys.
46
Photo by Jack Hursh
View to the south of downtown Reno and lenticular wave clouds.
wave cloud (Powell and Klieforth, 2000). Pilots need to be
cautious when flying near these clouds. Sailplane pilots,
however, can use the lift generated by the upper level wind
flow to achieve rapid ascents. They can remain aloft
sometimes for hours by using the upwardly moving air
near wave clouds to lift them again to higher altitudes. The
area downwind of the Sierra near Minden, Nevada is a
prime location for sailplane flights and many records have
been set by pilots flying in this region.
in the eastern foothills of the Sierra can reach
nearly hurricane force. Wind speeds of over 40 mph
with gusts to 80 mph or more have been reported at sites
all along the foothills and valleys east of the Sierra
during these strong wind events. Widespread damage can
result with fences blown down, shingles taken from
roofs, and vehicles (especially high-profile vehicles
traveling along north-south roads) blown off the road.
DUST STORMS AND SANDSTORMS
SYNOPTIC-SCALE WIND EVENTS
Dust storms and sandstorms are another danger from
strong synoptic-scale winds. Many climatological factors
contribute to the occurrence of dust storms. Landsberg
(1966) stated that wind is the most important factor,
because the “higher the wind velocity the more dust will
be carried, provided it is available.” An arid landscape is
necessary to provide this dust cover, and a period of
below-normal precipitation can contribute to the dry
conditions. A large area of fairly level ground is also
necessary because “mountains will tend to break the
force of the wind.” (Landsberg, 1966).
Ground cover such as sagebrush is sparse over much
of the western Great Basin and large areas of soil and
sand are exposed to the elements. Areas of dust are also
created when the water in shallow lakes evaporates. This
alkali residue is easily picked up by strong winds and
carried for miles. When this fine material becomes
airborne it can reduce visibilities to less than a quarter of
a mile. This can be especially dangerous to motorists
who may not see cars stopped ahead of them. Some of
the more intense sandstorms and dust storms can last two
to three hours, but most are fairly short-lived, usually
lasting no more than an hour.
Some of the most damaging winds in western Nevada are
not associated with strong thunderstorms. Large-scale
winds (referred to in meteorology as synoptic-scale winds)
are part of the general wind flow of the atmosphere. Winds
at the surface of the Earth are affected by topography
(ranging from hills to mountain ranges), trees, buildings,
and obstacles that block the wind flow or change its direction or speed.
However, above this friction layer, as it is called, the
wind flow is generally uninterrupted and high wind speeds
can be encountered just a couple of thousand feet above the
ground. If the lower atmosphere is unstable (with warmer
air near the surface and cooler air above it) the upper level
winds are more likely to mix down to the surface
(Whiteman, 2000). Across western Nevada this is more
common during the colder half of the year when Pacific
polar air masses invade the region.
A common scenario is when cold air moves in from
the northwest behind a cold front. The cold upper level air
moves across the Sierra Nevada and this cold dense air
then descends the eastern slopes of the Sierra. The air gains
speed as it rushes down the mountainside and wind speeds
47
Photo by Mark Vollmer
Lightning over the Carson Range, seen from the Tahoe Rim Trail, Mt. Rose Wilderness.
Convective Weather
by Brian F. O’Hara
water vapor in the air condenses into clouds. The warmer
the surface temperature, the faster and higher the air rises,
and this can cause clouds to develop to very high levels.
The tops of some of the more intense thunderstorms that
develop from these clouds rise to over 40,000 feet above
the surface (Figure 25).
During the summer, thunderstorms are usually widely
scattered so a particular location may not be affected by
them very often. Even during the summer, Reno only
reports thunderstorms an average of three days each month
(Figure 26).
Some locations are more conducive to thunderstorm
development than others. The Sierra Nevada seems to be a
preferred location for creating thunderstorms. Hill (1980)
found that “on non-Zephyr days there is a marked preference for thunderstorms to develop over the Sierra Nevada.
This is a reflection of the ability of these massive mountains
to act as an effective elevated heat source.” On days when
there is a Washoe Zephyr, Hill found that cumulonimbus
clouds (from which thunderstorms form) did not form over
the Sierra Nevada. The downslope winds associated with
Although not as active as many areas east of the Continental Divide, western Nevada gets its share of convective
weather. Afternoon thunderstorms can occur, mainly south
of the Reno area. Destructive winds can be a hazard. These
winds may be from a thunderstorm’s downdraft or from
strong upper level winds that mix down to the surface. Due
to the dry air mass typically over the region, hail is not a
significant hazard, but does occur on occasion. Tornadoes
are rare in Nevada, with the state averaging only about one
(generally weak) tornado per year. However, like any
tornado, when they do occur they can cause damage.
Lightning is another hazard that affects the public more
than most other thunderstorm-related hazards combined.
THUNDERSTORMS
Thunderstorms are fairly common across western Nevada
during the warmer half of the year. Even during winter
thunderstorms can occur if the air aloft is cold enough.
However, they are usually experienced from May through
September. The intense afternoon heating that occurs over
the region causes air to rise. This rising air cools and the
48
the Washoe Zephyr apparently inhibited the upslope winds
necessary to promote cumulonimbus development over the
Sierra crest (Hill, 1980). Hill also found that, on days
during which a Washoe Zephyr occurred, thunderstorm
development was more common over the Pine Nut Mountains. The westerly winds associated with the Zephyr may
contribute to the upslope winds in the Pine Nut Mountains,
helping thunderstorms to form.
THUNDERSTORM WIND GUSTS
Downdrafts from thunderstorms can exceed 50 mph, strong
enough to cause damage to structures. Trees can also be
damaged and even uprooted. A thunderstorm wind gust
might last ten minutes or less, a much shorter time than a
synoptic-scale wind event, but, with wind gusts approaching 80 mph, widespread damage could occur during that
relatively short time .
Most of western Nevada is sparsely populated and
most areas would not be damaged by thunderstorm downdrafts, except for a few uprooted trees. However, if a
strong thunderstorm occurred over a populated area such as
the Reno/Sparks metropolitan area or Carson City there
would be a greater chance that wind damage could result.
DRY MICROBURSTS
It is not necessary to have a thunderstorm in order to have
strong damaging winds. Strong downdrafts can be generated below high-based clouds that are common across the
Great Basin during the summer. In the warm dry air mass
typically over the region during the summer, cloud bases
are often over 10,000 feet above the ground, and they may
even be above the mountain tops (approaching 15,000
feet). Any rainfall that is generated in the cloud falls
through this very deep dry air mass.
Rain evaporates as it falls through dry air. This process
of evaporation cools the air. As more raindrops evaporate
the air continues to cool. This cool air quickly becomes
denser than the warmer air surrounding it and rushes to the
ground as a strong downdraft or downburst. When the
downdraft reaches the ground it spreads in all directions if
Figure 25. The development of a thunderstorm from
the cumulus stage (all updrafts within the storm)
through the mature stage (both updrafts and downdrafts) to the dissipating stage (all downdrafts).
Figure 26. Average number of days with thunderstorms at Reno, Nevada (1943–2004).
49
Photo by Kris Ann Pizarro
the air has fallen straight down. If the downdraft air hits the
ground at an angle it will tend to move in the general
direction it was traveling when it reached the surface.
If the outflow wind from a downburst extends more
than 2.5 miles from its point of contact with the ground it is
classified as a macroburst. If the wind outflow extends 2.5
miles or less from its origin it is called a microburst
(Fujita, 1985). If measurable rain is recorded with the
microburst it is called a wet microburst. However, over the
dry Great Basin, very little rainfall reaches the ground.
Microbursts over western Nevada are usually dry microbursts. However, microbursts are not confined just to dry
areas of western Nevada. On September 13, 1987, a microburst occurred over Lake Tahoe. As described in the
publication Storm Data, a “microburst from dissipating
thunderstorms in the Zephyr Cove area of Lake Tahoe
estimated at 60 to 70 mph damaged a few sailboats.” (USDC, 1987).
Wind speeds in dry microbursts can reach speeds
similar to those in thunderstorm downdrafts. Damage can
result as wind speeds of well over 50 mph travel across the
area. However, damage patterns are different than those
caused by tornadoes. A tornado creates a fairly narrow
damage path with evidence of rotation evident across the
ground. Damage patterns from microbursts have a radial
pattern as the straight-line winds move away from the point
of contact with the ground. Evidence of these straight-line
winds can be seen as trees and other objects are all blown
down in the same direction.
HAIL
Large hail is not common in western Nevada. Flora (1956)
stated that in “twenty-five years the only Nevada loss of
consequence reported to the Weather Bureau was $39,000,
caused by a hailstorm on July 21, 1943, in Fernley and the
surrounding area.”
It is probable that hail forms in many of the thunderstorms that occur over Nevada, especially the stronger
storms. However, large supercell thunderstorms (which
would generate the largest hailstones) do not often form
over the Great Basin due to the lack of moisture over the
region. Also, because of the hot, dry ground across the
Great Basin, clouds that form tend to have high bases,
sometimes over 10,000 feet above the surface. Hailstones
that do form in thunderstorms tend to melt as they fall
through the dry air mass below the cloud base. Only the
largest hailstones would not completely melt before reaching the ground. This is why hailstones that reach the
ground in western Nevada are relatively small, usually less
than an inch in diameter, and often much smaller than onehalf inch in diameter.
There have been more reports of hail in western
Nevada during the late 1980s and 1990s. This is probably
due to increased efforts of National Weather Service
personnel in soliciting and verifying reports of not just hail
but any occurrence of severe weather. Since the early
1960s, 26 hail events across the region were reported in the
publication Storm Data (USDC, 1959–2005).
Dust devil.
TORNADOES
Tornadoes are rare in Nevada, which averages about one
tornado a year and these tornadoes are usually weak. From
a review of Storm Data, since the early 1960s only 12
tornadoes have been reported in extreme western Nevada
(USDC, 1959–2005). However, due to the sparse population in the rural areas it is probable that many more
tornadoes have occurred, although, with the lack of
supercell thunderstorms climatologically, these tornadoes
most likely would have been relatively weak (F0 or F1 in
intensity). According to newspaper accounts a tornado was
also reported in Reno on April 1, 1949.
Unlike tornadoes, waterspouts do not form from
cumulonimbus (thunderstorm) clouds. Waterspouts form
from cumulus clouds, and they are weaker than tornadoes.
However, they can occur over larger lakes such as Lake
Tahoe and Pyramid Lake, mainly during the summer, and
can damage boats that venture too close to them.
50
reported in Storm Data, a dust devil in Gardnerville, Nevada
on April 21, 1997 “lifted a 3 year old child a half foot off the
ground and knocked over a swing set.” (USDC, 1997).
FUNNEL CLOUDS
A tornadic circulation that does not reach the ground is
called a funnel cloud. These are generally short-lived, and
most of the funnel clouds observed in the eastern Sierra
and western Nevada generally last five minutes or less
before ascending back into the cloud base.
LIGHTNING
Lightning is associated with thunderstorms. In fact, thunder
is the sound produced by the expansion of the rapidly
heated air around a lightning bolt (Uman, 2001). Lightning
should always be considered dangerous, and anyone who
sees lightning or hears thunder should seek shelter until the
thunderstorm has passed. Lightning bolts can extend up to
10 miles from their parent thunderstorm. So, even if a
storm appears to be far away, it may still be close enough
to be dangerous.
Lightning can cause damage to buildings and can start
fires in many types of vegetation. People can be injured or
killed if they are struck by lightning. Livestock can also be
struck and killed since they often are on open rangeland in
the West. Lightning occurs many times during the summer
thunderstorm season in western Nevada. Since the early
1960s, the publication Storm Data has listed 15 incidents in
which lightning caused damage or injured people in the
Reno-Carson City-Lake Tahoe region, but, no deaths were
reported with these events. Most of these events, as might
be expected, occurred during the late afternoon and evening
when thunderstorms are most common across the area.
DUST DEVILS
Photo by Mark Vollmer
Dust devils are sometimes mistaken for tornadoes but they
are quite different. While tornadoes form as a result of
strong rotating winds inside of cumulonimbus clouds, dust
devils form at ground level as a result of strong surface
heating. The circulation that forms at ground level then
develops upward (Flora, 1953).
In western Nevada, dust devils occur mainly during
summer afternoons. Ground that is bare or has very little
vegetation can heat rapidly during the day. Even if the air
temperature at observation level (around 5 feet) is in the
90s, the temperature at ground level can be even higher.
This very warm air at ground level, being less dense than
the cooler air above it, moves upward and cooler adjacent
air at ground level flows in to replace it. The circulation
that develops can reach 1000 feet or higher. Dust devils are
never as strong as tornadoes, but they can cause slight
damage by knocking over lawn furniture or trash cans. As
Evening thunderstorm over distant Pine Nut Mountains. View across Washoe Valley and
the Virginia Range from the Mt. Rose Highway. Lights of Washoe City can be seen in the
near distance.
51
Photo by Jeremy Vlcan
Waterfall fire. View toward Lakeview Hill from about halfway through Washoe Valley, July 2004.
Wildfires
by Brian F. O’Hara
Because of the dry air mass over the high desert of the
Great Basin, thunderstorms typically produce very little
rainfall that reaches the ground. Thus these thunderstorms
are referred to as dry thunderstorms, and usually occur
during the warmer half of the year. Lightning strikes from
these thunderstorms occasionally start wildfires, but some
wildfires are caused by human carelessness. Davis (1959)
states that outbreaks “of forest fires, both in size and
number, tend to occur with hot weather or in periods when
the prevailing temperatures are above normal.” The fire
season in western Nevada and the Lake Tahoe region
generally runs from mid May to mid October.
During the spring and early summer natural vegetation
dries out and, by May or June, plants such as grasses and
sagebrush may contain very little moisture. As a result, the
fire danger associated with these plants is very high. A fire
can easily start if a lightning bolt strikes dry plants such as
these. Thunderstorms during the fire season are often
caused by monsoon moisture that moves into the region
from the south, and also by low pressure systems over the
region. The air mass over the region during the summer
tends to be hot and dry with significant low-level instability (Schroeder and Buck, 1970).
Prolonged drought can increase the possibility of fires
growing large “because drought dramatically decreases the
moisture content of both live and dead fuels (Whiteman,
2000). Due to the dryness of the vegetation the resulting
fire can spread rapidly. If this occurs near a populated area
it becomes critical that the fire is extinguished as quickly as
possible. This was true during the Waterfall Fire, which
burned over 7500 acres near Carson City in July 2004.
Many homes and outbuildings were destroyed, but the fire
was kept out of Carson City itself.
The Washoe Zephyr winds that occur during the
afternoon can drive a fire and make it grow rapidly. However, any strong wind can help to drive fires out of control.
A fire in Reno on March 2, 1879 destroyed many buildings
and left hundreds of people homeless. It apparently started
from a burning stove pipe which set a pile of wood on fire.
The Reno Weekly Gazette (March 6, 1879) reported that
the “wind was blowing hard from the southwest and fanned
the spark into instant conflagration.” Most of the buildings
in the city were made of wood so the fire had plenty of fuel
to feed on as it moved east. The newspaper reported that 50
acres of businesses were destroyed.
52
Perhaps the worst fire in the region’s history was the
one that destroyed Virginia City on October 26, 1875.
Most of Nevada’s then-largest city was burned to the
ground, extending from the Comstock mines in the north to
the south edge of town, and from Washington Street in the
west to the east edge of town. The wooden buildings were
tinder dry and ignited instantly. Strong wind “set the
disaster in motion when it carried the flames to roofs
downhill” (James, 1998). The Virginia City Territorial
Enterprise (October 27, 1875) reported that the fire started
in a lodging house on A Street. The paper went on to say
that a “breath of hell melted the main portion of the town to
ruins” (James, 1998). Not only wooden structures, but
brick buildings were destroyed. Scores of buildings (with
their entire contents) were burned. Total damage was
estimated at between $5 million and $10 million (in 1875
dollars) (Elliott, 1987).
Like the Waterfall Fire, another wildfire threatened
Carson City, this time from the south. On September 28,
1926, a wildfire started in Clear Creek Canyon, west of
Stewart, Nevada, south of Carson City. The Reno Evening
Gazette (September 28, 1926) stated that, because of an
early morning breeze, the fire “rushed up [Clear Creek]
canyon, crossed the road at Swift’s station and then the
wind changed and became stronger and scattered the
flames in all directions.” The wind forced the fire toward
Lake Tahoe and Carson City, and smoke from the fire
could be seen in Reno. The fire continued into the next day
before it was contained. Tragically, five men died while
fighting the fire when they were trapped in Clear Creek
Canyon and could not escape the flames.
In late August 1960 the Donner Ridge Fire affected
the region. As a result of this fire, Reno was without
electricity for four days. During 1973 many fires raged
from the Reno-Sparks area, to just
east of Placerville, California, and
Table 6. Major wildfires in the Reno-Carson City-Lake Tahoe Area (1999–2005).
south to Gardnerville. Fires during
September 1981 burned much of the
Lightning (L)
Date under
Location
Acreage
eastern slope of the Carson Range
Name of fire
or Human
control
(county/counties)
burned
above Washoe Valley, and near the
(H) caused
Mt. Rose Highway in the Whites
Fish Complex
Aug 29, 1999
Washoe
47,633
L
Creek-Galena Forest area.
Reno Complex
July 2, 2000
SW Washoe
18,080
L
The erratic winds associated
with many fires make them very
Ramsey
July 4, 2000
E Douglas
5,666
L
difficult to bring under control. This
Seneca
July 11, 2000
SW Washoe
1,110
H
is why it is extremely important that
there is defensible space around
Cold Springs
July 25, 2000
SW Washoe
400
H
houses and other buildings. Residents
Red Rock
Aug 3, 2000
SW Washoe
2,203
L
can make their properties more fire
resistant by reducing the amount of
Arrow Creek
Aug 4, 2000
SW Washoe
2,900
L
vegetation next to their homes. The
Sutcliffe
Aug 4, 2000
S Washoe
300
L
use of decorative rock and other
forms of xeriscaping can help to
Right Hand
Aug 14, 2000
S Washoe
452
L
reduce the amount of flammable
Siegel
May 15, 2001
E Douglas
800
L
material near buildings. Some of the
Warrior
May 30, 2001
SE Washoe
6,508
L
largest fires in the Reno-Carson CityLake Tahoe region from 1999
E Nevada and SW
Martis
July 1, 2001
14,500
H
through 2005 are listed in Table 6.
Washoe
Pleasant Valley
Aug 11, 2001
SW Washoe
775
L
Antelope
Aug 11, 2001
S Washoe
900
L
Fish
Aug 15, 2001
SE Lassen and W
Washoe
21,343
L
Cannon
June 28, 2002
Douglas and Mono
22,750
H
Gondola
July 6, 2002
E El Dorado
670
H
Highway 50
June18, 2003
SW Washoe
575
H
Robb
July16, 2003
SW Washoe
2,196
H
Waterfall
July 20, 2004
Carson City SW
Washoe
8,700
H
53
Floods
by Gary Barbato
Winter rain and snow in the eastern Sierra Nevada
provide the region with almost all of its streamflow, as well as its reliable water supply. Runoff
from steady spring and early summer snowmelt is
stored in Lake Tahoe and the many other lakes
and reservoirs throughout the Sierra and western
Nevada so that residents of the region have a
sufficient water supply during the summer dry
season. Although strong thunderstorms with heavy
rainfall can develop during the summer, warm
season precipitation is typically light, spotty, and,
compared to winter precipitation, rare. Summer
drought is common and expected throughout
northern California and western Nevada.
The heaviest winter precipitation falls in the
region during what is sometimes called a
"Pineapple Express" or "Pineapple Connection."
How this scenario typically develops is diagrammed in Figure 27. About a week to 10 days
before the heavy precipitation occurs on the west
coast of the United States, heavy rain is occurring
over the far western tropical Pacific, and a moisture plume from this precipitation begins to extend
northeast. There is a strong polar jet moving
clockwise around high pressure over the Gulf of
Alaska. By about three to five days before the
heavy precipitation, the heavy rain in the tropical
Pacific has moved east, and the moisture plume
now extends farther northeast toward the west
coast.
The high pressure over the Gulf of Alaska has
weakened and moved westward, and is now
centered over the Aleutian Islands. A low pressure
trough has begun to develop over the eastern Gulf
of Alaska, and the jet stream has split into two
equally strong branches. One branch continues to
move clockwise over the Aleutian High, but a
southern branch of the jet stream is now set up
south of the high pressure area and the low pressure trough over the Gulf of Alaska, and is in
position to push the moist air directly into the west
coast of the United States. By the time the heavy
precipitation arrives at the west coast, the trough
of low pressure over the northeastern Pacific
Ocean (now called the “Aleutian Low”) has
become large, deep and strong. The stream of
warm, moist, unstable subtropical air extends
from Hawaii all the way to just south of the
Aleutian Low. Cool moist air from the Gulf of
Alaska causes a series of fronts to move out of the
Aleutian Low toward the California coast, which
can then cause prolonged heavy precipitation in
the region.
Figure 27. Typical wintertime weather patterns preceding west
coast heavy precipitation events. Map courtesy of the NOAA
Climate Prediction Center.
54
Rain-on-snow type flooding is characterized by sharp
rises and high peak flows, usually with slow recessions.
Flooding may occur on all rivers originating in the eastern
Sierra at the same time, although the magnitude of flow
can vary greatly from one river to another, depending on
the location, elevation, temperature (or snow level) and
intensity of the precipitation. The travel time of a flood
wave from the headwaters to the valley areas can range
from just 3 or 4 hours on the Susan River, to 6 to 10 hours
on the Truckee (from Tahoe City to Reno), to about 24
hours on the Carson River (from headwaters upstream of
Markleeville and Woodfords, California to Carson City), to
about 2 to 3 days from the headwaters of the Walker River
(above Bridgeport and Coleville, California) to the Mason
Valley (Yerington, Nevada) area. The flood wave on the
Walker may take over a week to travel down from the
headwaters to Walker Lake. Walker River flood crests
dissipate significantly below Bridgeport and Topaz Lakes
as they traverse the broad Mason Valley.
Even though flooding in the headwater areas usually
results in valley flooding, this is not always the case,
especially if there are only isolated areas of heavy precipitation, or if most of the precipitation does not make it very
far over the Sierra crest. In December 1964, January 1969,
January 1970, March 1971, January 1980, and February
1982, flooding was much worse in the headwater areas
than in the valleys, which, in many of these cases, had only
minor flooding .
When Pacific storms do make it over the Sierra crest
and snow levels are below about 7000 feet, flooding can be
much worse in the valley areas than in the headwaters
because: (1) there is no runoff in the headwaters because it
is snowing; and/or (2) a large snowpack at the higher
elevations soaks up much of the rainfall; and (3) a large
low elevation snowpack melts, adding to runoff in the
lower elevations. These three scenarios result in little
runoff from the headwater areas, but there can be tremendous amounts of runoff from the lower portions of the
basins. The February 1986 and December 2005 floods
were good examples of this, with much of the flooding
occurring on lower tributaries of the mainstem rivers.
Prolonged minor to moderate flooding over a large
area may be caused by a rapidly melting large snowpack in
spring and early summer on rivers and streams without
large reservoirs in the headwaters. This would include the
Carson River above Lahontan Reservoir and the West and
mainstem Walker Rivers. Snowmelt floods are not considered a problem on the Truckee River through the Truckee
Meadows due to upstream reservoir regulation. Snowmelt
floods are largest during years with extremely large
(greater than 150% of average on April 1) mid- to highelevation snowpack water equivalent, and occur during a
rapid warm up, usually from mid April to mid June, or
even as late as early- to mid July on the Walker River
basin. Snowmelt floods have extremely large volumes and
may last for many days or even weeks as the snow melts,
but the flood crests and resulting damages are far less than
the rain-on-snow floods which can occur during the winter.
Also, these types of floods are far easier to forecast than
rain-caused floods because they are driven by warm
temperatures.
The Sierra Nevada has a major effect on the hydrology
of western Nevada. This mountain range effectively blocks
most precipitation from reaching areas to the east. Western
Nevada is in the rain shadow of the Sierra, and most of the
precipitation occurs west of the crest. Significant precipitation does get into the Lake Tahoe basin and the higher
elevations on the east sides of the Sierra Nevada and the
Carson Range, but only a small percentage makes it into
the lower elevations of western Nevada. So, the large,
usually reliable snowpack and reservoirs in the eastern
Sierra Nevada are able to supply dry western Nevada with
most of its water supply.
Huge amounts of snow can fall in the upper reaches of
the eastern Sierra Nevada. Snow depths of over 10 feet are
common at the higher elevations, though depths of over 25
feet are relatively rare. At Donner Summit (elevation 7239)
on the crest of the Sierra Nevada, snowpack depths equaled
or exceeded 25 feet only six times since records began in
1879 (1879–80, 1889–90, 1894–95, 1906–07, 1910–11,
and 1951–52). The maximum depths were recorded during
the winters of 1879–80 and 1889–90, when over 31 feet
was on the ground. Total snowfall has exceeded 60 feet at
Donner Summit during the winters of 1879–80, 1889–90,
1937–38, and 1951–52. The winter of 1937–38 had the
largest snowfall, with over 68 feet (819 inches) recorded
(Osterhuber, 2001). However, snow depth at Donner
Summit is not always a foolproof way to measure total
annual precipitation because during many winters much of
the precipitation may fall as rain.
RIVER FLOODS
Western Nevada and the eastern Sierra Nevada have a long
history of infrequent, but very damaging river flooding,
with accounts dating back to December 1852. Mainstem
river flooding has occurred only between the months of
November and May. Although summer thunderstorms can
cause heavy precipitation and isolated flash flooding on
creeks and streams during the summer, the total amount of
runoff is insufficient to bring rivers to flood stage. The
largest regional floods occur between November and
March and are usually caused by prolonged warm, heavy
rain falling on a large snowpack or frozen or saturated
ground during the winter. However, having a large snowpack is not a prerequisite for flooding during an intense,
prolonged, warm winter storm. These storms can produce
massive amounts of precipitation which can lead to flooding without much of a snowpack over the region, especially
if soils are saturated due to a wet autumn. Nevertheless,
heavy rainfall on a significant snowpack at all elevations,
from the western Nevada valleys up to the higher elevations of the Sierra, often leads to the most serious flooding.
Generally, a foot of snow at the 5000-foot elevation in the
eastern foothills of the Sierra would be considered significant; at higher elevations, over 120% of average snowpack
water equivalent is significant. All of the region’s largest
floods have resulted from a prolonged warm rain-on-snow
weather pattern.
55
(1996, 1997a, 1997b, 1997c); Osterhuber (1993, 2001);
U.S. Army Corps of Engineers (USACE) publications,
data, and correspondence (1970, 1972, 1974, 1980, 1983,
1997); U.S. Department of Commerce (USDC) (1997);
U.S. Geological Survey (USGS) publications (1954, 1958,
1960, 1982, 1991); USGS Fact Sheets (FS-077-97, FS-12397, FS-183-97, FS-005-98); and correspondence (R.E.
Bostic, personal communication, 2007; R.A. Hunrichs,
personal communication, 2007). Much of the information
about the January 1997 flood was obtained by NWS Reno
office staff after the flood (Barbato and Hickman, 1997).
The historical information about these past floods was
derived by the above authors from such sources as available streamflow records, newspaper files, historical documents, interviews with local residents, and from photographs of these past floods.
LARGEST HISTORICAL FLOODS IN WESTERN
NEVADA AND THE EASTERN SIERRA NEVADA
Despite the fact that western Nevada is very dry and is in
the rain shadow of the Sierra Nevada, major river floods
have occurred here and in the eastern Sierra, although they
are not frequent. The fact that they are infrequent sometimes causes the area’s population to forget their significance and danger in the long periods between major floods.
This has led to disastrous results in the past, as residents
continue to build in the floodplains of the rivers and
streams during the long periods between major floods.
Table 7 lists the largest floods of record in the eastern
Sierra and western Nevada.
Following are descriptions of some of the major raininduced floods that have occurred along the Truckee,
Carson, and Walker Rivers since the first EuropeanAmerican settlers began arriving in the 1850s. Most of the
flood information in this section was obtained from excellent accounts put together by Rigby and others (1998);
Altine and Dunn (1997); the USDA Nevada River Basin
Survey Staff (1969); Goodwin (1977a, 1977b); Horton
December 24–30, 1852. The earliest record of flooding in
western Nevada was made by the settlers of Genoa in
Carson Valley, Nevada’s first European-American settlement. Beginning about Christmas Eve, heavy snow fell in
the Carson Valley for two days and piled up to 3 feet deep
on the valley floor. This was followed by four days of
warm rain, melting all of the snow,
and inundating the Carson Valley by
December 30. The flooding was
extensive, but damage was minor as
Third highest flow
the population was well away from
cfs (date)
the low areas of the valley. Nothing
is known about flooding in other
portions of western Nevada at this
time, due to the lack of population
2,740 (3/8/1986)
(Rigby and others, 1998). Based on
the limited description of the magnitude of flooding, it was probably
7,760 (12/23/1955)
greater than a 50-year flood on the
Carson River.
Table 7. Largest floods of record.
Station
Highest flow
Second highest flow
cfs (date)
cfs (date)
Lake Tahoe and Upper Truckee River basins
Upper Truckee R.
at S. Lake Tahoe
5,480 (1/2/1997)
2,850 (12/31/2005)
Truckee River basin
Truckee
11,900 (1/2/1997)
11,000 (2/1/1963)
Farad
17,500 (11/21/1950)
15,500 (12/11/1937)
15,300 (3/18/1907)
Reno
20,800 (12/23/1955)
19,900 (11/21/1950)
18,800 (3/26/1928)
2,090 (1/1/1997)
1,000 (1/31/1963)
Steamboat Creek
3,600 (2/17/1986)
3,600 (12/31/2005)
Vista
18,900 (2/1/1963)
18,500 (1/2/1997)
16,100 (2/18/1986)
Wadsworth
(below Derby Dam)
19,700 (1/3/1997)
18,400 (2/1/1963)
16,900 (2/19/1986)
Gardnerville
20,300 (1/3/1997)
17,600 (12/23/1955)
Woodfords
8,100 (1/1/1997)
Carson City
30,500 (1/3/1997)
30,000 (12/24/1955)
21,900 (2/1/1963)
Ft. Churchill
22,300 (1/3/1997)
20,000 (3/19/1907)
16,600 (2/19/1986)
6,220 (11/20/1950)
5,800 (12/11/1937)
Carson River basin
13,400 (2/1/1963)
4,890 (2/1/1963)
4,810 (12/23/1955)
West Walker River basin
Coleville
12,300 (1/2/1997)
56
December 20, 1861–January 2,
1862. Up to 2 feet of heavy, wet
snow fell on the valley floors the
week before Christmas, 1861. This
was followed by a period of extremely cold weather, which turned
the wet snow into sheets of ice. From
Christmas Day to December 27,
heavy, warm rain fell and eventually
melted the icy snow, causing extensive flooding. The Carson Valley
became a lake, but luckily very few
of the people living there at the time
were located near the river, and little
damage was reported.
In both
Empire (east of Carson City) and
Dayton (the third largest town in
Nevada Territory at the time),
drownings were reported and buildings were washed away (Rigby and
others, 1998; and Goodwin, 1977a).
Just above Dayton, the Island Stamp
57
Photo courtesy of the Nevada Historical Society
Mill floated off its foundation. Two
people drowned trying to escape. The
bridge over the Carson at Dayton was
destroyed, and floodwaters reached well
up into the town (Goodwin, 1977a).
This was the earliest damaging
flood on record in the Truckee Meadows. Along the Truckee River, all
settlements were either destroyed or
flooded, and the Truckee Meadows
became a huge lake. All bridges over the
Truckee from Verdi to Glendale (in
present-day Sparks, near where Steamboat Creek enters the Truckee) were
destroyed. This included the bridge built
by Charles Fuller in 1859 at the future
site of the Virginia Street bridge in
Reno. No measurements were available, but based on the description of the Flood waters at Virginia Street bridge in Reno during flood on March 18, 1907.
flood it was probably between a 50and a 100-year flood event on both the Carson and Truckee
Severe flooding occurred on the Truckee and Carson
river basins.
Rivers, though flooding was not as damaging on the
Walker River. The flooding was caused by heavy rain
December 20, 1867–January 3, 1868. This flood again
falling on a fresh, heavy late season snow cover which
turned the Carson Valley and Truckee Meadows into huge
extended to the valley floors (Rigby and others, 1998), as
lakes, exceeding the flood crest set in December 1861well as on frozen or saturated ground (Horton, 1997b). The
January 1862, as well as the amount of damage, as more
runoff combined with snowmelt and the Truckee, Carson,
people were in the region by this time due to the Comstock
and Walker Rivers quickly rose.
mines. It was caused by two prolonged, unseasonably
Many square miles of the Truckee Meadows were
warm rain-on-snow events in the Sierra Nevada which
flooded by the Truckee River, from Vista west to Sparks,
occurred from December 20, 1867 to Christmas Day, 1867,
and south along Steamboat Creek beyond Boynton Slough.
and from December 30, 1867 to January 2, 1868. All
The entire community of Glendale was evacuated during
bridges in the Carson Valley were swept away, including
the flood (Goodwin, 1977b; USACE, 1970). The Virginia
William Cradlebaugh’s toll bridge, the first bridge over the
mainstem Carson River in Carson Valley. In the Truckee
and Truckee Railroad bridge over Galena Creek in Pleasant
Meadows, both Glendale (east of present-day Sparks) and
Valley was washed out, and the Electric Light Bridge near
Lake’s Crossing (now Reno) were flooded and the bridges
Booth Street and several other bridges in Reno were
in those towns were destroyed. This flood caused the
severely damaged (Rigby and others, 1998). South of the
Central Pacific Railroad to select Lake’s Crossing as their
Truckee River, the Truckee Meadows flooded from the
Truckee Meadows station site instead of (at the time) the
Virginia Range foothills westward to the Huffaker Hills. A
much larger Glendale (Goodwin, 1977b). No measurements
16-year old boy attempting to rescue a person from a tree
were available, but based on the description of damages, it
on an island was drowned when his boat overturned
could have been as great as a 100-year flood.
(USACE, 1970).
The 1907 flood ranks as the last recorded flood that
March 16–23, 1907. This was the early “benchmark” raincaused severe damage along the entire length of the Caron-snow flood in western Nevada, against which all those
son, from its headwaters above the Carson Valley downcoming later in the twentieth century would be compared.
stream to the former Churchill County seat of Stillwater,
It is the first major flood in the region for which there are
just west of Stillwater Marsh. This was because Lahontan
some streamflow records, and ranks at least equally with
Dam was not completed until 1915. Fallon was established
the two great nineteenth-century floods in 1861–62 and
in 1896, and parts of the town were severely flooded for
1867–68 (Goodwin, 1977b). Instantaneous flow records do
the first and only time in its history, because Lahontan
not exist for the Truckee River at Reno for this flood.
Dam was not yet protecting it (Goodwin, 1977a). “Every
However, if the estimate by the USACE of the peak flow
bridge on the Carson (River), from the Sierra Nevada to the
for this flood at Reno is believed, it ranks as the fourth
Humboldt-Carson Sink was destroyed during the 1907
largest flood of record on the Truckee River at Reno. It was
flood” (Goodwin, 1977a). This included the Virginia &
estimated by the U.S. Department of Agriculture, Natural
Resources Conservation Service that "under similar condiTruckee Railroad bridge and the McTarnahan Bridge, both
tions of settlement and development, this flood event most
of which connected Carson City with Minden, and both of
likely would have at least equaled the devastating floods of
which had just been completed a few months before the
1950 and 1955 and exceeded the recorded damage of the
flood. The Cradlebaugh Bridge, located near where the
flood of December 1937." (Horton, 1997b).
present U.S. Highway 395 bridge crosses the Carson River,
March 23–28, 1928. The Truckee River
was most affected by this flood, which
is estimated to have been about as
severe as the March 1907 flood at Reno,
and ties for the third worst flood on
record there. However, flooding on the
Carson River was not nearly as severe
as in the 1907 flood. When this storm
began on the 23rd as a snowstorm, it was
hailed as a “drouth-breaker” because the
winter season had, up until late March,
been dry. By March 25, residents in the
lower Truckee Meadows along the river
were evacuating due to severe flooding Truckee River flooding, Reno; March 1928.
(Goodwin, 1977b). Several thousand
Chestnut Street (now Arlington Avenue) bridge was
acres of lowlands along the Truckee River were flooded,
damaged to such an extent that it had to be replaced. Log
especially from Sparks downstream to Vista. The Truckee
jams and debris deposited on the upstream sides of bridges
Meadows “Lake” grew to “a better than seven-mile arc at
had to be broken up by blasting. Ranching areas were
the western base of the Virginia Range” by March 27
hardest hit, with the loss of livestock and pasture. About
(Goodwin, 1977b). Residents and livestock along the river
500 people in the Reno-Sparks area were made homeless
were evacuated, as roads, bridges, and homes were subby the flood (USACE, 1970). Table 10 lists flood flow data
merged. A few refused to evacuate, and they later had to be
for the December 1937 flood.
rescued by boat. One and a half miles of the newly comNovember 13– 23, 1950. Flooding during mid November
pleted U.S. Highway 40 between Sparks and Vista were
1950 caused widespread damage on the Truckee, Carson,
submerged to a depth of one foot. As reported by Goodwin
and Walker Basins, and was the largest flood in the region
(1977b) “the Truckee went on a rampage through Reno and
since streamflow records began (USACE 1970). The flooding
the Truckee Meadows, which was unequaled since 1907.”
was caused by “a sequence of rapidly moving storms and
Table 9 lists flood flow data for the March 1928 flood.
unseasonably high temperatures that melted most of the
December 9–14, 1937. Warm rain falling from the evening
early snowpack in the Sierra Nevada.” (Rigby and others,
of the 9th through the evening of the 11th melted much of
1998). Like previous rain-on-snow events, snow levels
the mountain snowpack. The Truckee, Carson, and Walker
averaged between 8000 to more than 10,000 feet during
th
Rivers were out of their banks by the 11 (Goodwin,
much of the precipitation period. Adding to the problem
1977b). Downtown Reno was flooded by the Truckee
was that soils were extremely wet before the November
th
River on the 11 and the Truckee Meadows became a vast
storms, due to 300 percent of normal precipitation throughlake from near what is now the U.S. Highway 395 Bridge
out the area in September and October 1950 (USGS, 1954).
near the Grand Sierra Resort (formerly Reno Hilton) east to
the Glendale/Vista area, and south along Steamboat Creek
Table 9. March 1928 flood flow data.
through December 14 (Rigby and others, 1998). The
Station
Table 8. March 1907 flood flow data.
Station
Date
Peak or
Average Daily
Flow (cfs)
Event
Magnitude
Date
Event
Magnitude
Truckee River basin
Truckee River basin
Farad
3/25/1928
12,000
35-year
Reno
3/26/1928
18,800
40-year
3/28/1928
12,000
15-year
3/26/1928
2,570
2-year
Ft. Churchill 3/28/1928
2,710
2-year
Farad
3/18/1907
15,300
70-year
Wadsworth
Reno
3/18/1907
18,500
40-year
(below Derby
Dam)
Vista
3/18/1907
10,000
10-year
Carson River basin
20,000
175-year
Carson River basin
Ft. Churchill 3/19/1907
Peak or
Average Daily
Flow (cfs)
Gardnerville
58
Photo courtesy of the Nevada Historical Society
was washed away despite the fact that it
had been rebuilt and strengthened after
it had been washed away in 1890. The
Southern Pacific Railroad bridge just
west of Fallon also was destroyed.
Table 8 lists flood flow data for the
March 1907 flood.
Station
Table 10. December 1937 flood flow data.
Station
Date
Peak or
Average Daily
Flow (cfs)
Event
Magnitude
Date
Peak or
Average Daily
Flow (cfs)
Event
Magnitude
Truckee River basin
Truckee River basin
Truckee
11/20/1950
6,480
20-year
Farad
11/21/1950
17,500
100-year
Farad
12/11/1937
15,500
70-year
Reno
11/21/1950
19,900
50-year
Reno
12/11/1937
17,000
35-year
Vista
11/21/1950
8,750
10-year
Vista
12/12/1937
9,760
10-year
11/22/1950
9,180
8-year
Wadsworth
(below Derby
Dam)
12/13/1937
8,970
Wadsworth
(below Derby
Dam)
8-year
Carson River basin
Carson River basin
Gardnerville
11/21/1950
12,100
35-year
11/20/1950
4,730
60-year
Gardnerville
12/11/1937
10,300
25-year
Woodfords
Woodfords
12/11/1937
3,500
30-year
Carson City
11/22/1950
15,500
25-year
Ft. Churchill
12/14/1937
5,500
8-year
Ft. Churchill
11/23/1950
7,850
15-year
6,220
40-year
Walker River basin
Walker River basin
Coleville
12/11/1937
5,800
Coleville
30-year
59
11/20/1950
Photo courtesy of the Nevada Historical Society
Total damages on the Truckee,
Carson, and Walker basins were $4.4
million ($37.5 million in 2007 dollars). Of this amount, $1.98 million
($16.9 million in 2007 dollars) was in
the city of Reno (Rigby and others,
1998; USACE, 1970; and USGS,
1954). Over 41,000 acres were
flooded on the Truckee, Carson, and
Walker Basins, with 33,000 acres of
this total in the Carson River basin
(USGS, 1954). Two deaths were
reported, and the American Red Cross
assisted about 200 persons who were
evacuated from their homes (Rigby
and others, 1998), and at least 15
families were left completely homeless (USGS, 1954). Two men and two
patrolmen on duty were reported to
have been carried off U.S. Highway
40 (now Interstate 80) and down a
steep embankment by a slide in the
Truckee Canyon (USGS, 1954), and
U.S. Highway 40 in the Truckee Floodwaters covering the Sierra Street bridge in Reno during the November
Canyon was closed for more than a 1950 flood.
week after the flood. Residents of
Floriston in the Truckee Canyon were isolated except for a
In the Truckee River basin, floodwater covered much
footbridge when the bridge crossing the river was washed
of downtown Reno, and extended from West Second Street
out. Also destroyed were several sections of U.S. Highway
on the north to Mill Street on the south (USACE, 1970),
395 in the West Walker Canyon south of Coleville (USGS
and was 4 feet deep on the main floor of the Riverside
1954). At least six bridges on County or State secondary
Hotel (Rigby and others, 1998; USACE, 1970). All bridges
routes in the Gardnerville-Markleeville-Coleville area were
across the Truckee were closed, and the Rock Street Bridge
washed out and others were in danger of failing (USGS,
was destroyed. Water was 3 feet deep in much of down1954). Lake Tahoe rose an amazing 1.89 feet from Novemtown Reno, with velocities high enough to move parked
ber 13 through December 6, an increase of about 193
cars, and several were tipped over by the raging currents
square miles of lake surface, or 233,000 acre feet. Pyramid
Lake rose 1.7 feet from November 15 through December
Table 11. November 1950 flood flow data.
10 (USGS, 1954).
Photo courtesy of the Nevada Historical Society
(USGS, 1954). About 6,300 acres
were flooded in the Truckee basin,
mostly between Reno and Vista
where about 3800 acres of agricultural land was flooded (USGS,
1954). Livestock were drowned,
crops destroyed, homes were damaged or destroyed, and irrigation
facilities were washed out. News
reports at the time told of a dike built
by the city engineer of Sparks that
prevented flooding in three quarters
of town (USGS, 1954). Total damages on the Truckee River basin
were $3.2 million in 1950 dollars,
about $27.3 million in 2007 dollars
(Rigby and others, 1998; USGS,
1954). The largest losses were by
businesses adjacent to the Truckee in
Reno, where department stores,
furniture stores, auto sales lots,
theaters, the U.S. Post Office, and
the two largest hotels in the city
were heavily damaged (USGS,
1954). Table 11 lists flood flow data
for the November 1950 flood.
Downtown Reno flooded during December 1955.
Precipitation Frequency Atlas of the United States, a 1000year 7-day rain for this area is about 8 inches! (Bonnin and
others, 2003).
The degree of flooding was worse in 1955 than in 1950
in most instances (the main exception being the Truckee
River at Farad), with this being the record flood at Reno.
Nearly 100,000 acres were flooded on the Truckee, Carson,
and Walker Basins, more than double the 1950 flood
(Rigby and others, 1998) However, damage was not as
severe as that experienced from the 1950 flooding, as some
flood mitigation and preparation measures had been put in
place in the region during the intervening five years
(USACE, 1970, 1983). The total estimate of damages on the
Truckee, Carson, and Walker river basins was $4 million
(1955 dollars; about $30.7 million in 2007 dollars) (Rigby
and others, 1998).
On the Truckee River basin, there was extensive
flooding in Truckee where the Truckee River crested at
7760 cfs (cubic feet per second) on the 23rd, the third
largest flood of record at this location. In Reno, the Riverside and Mapes Hotels, located next to the Truckee River
on Virginia Street, set up sandbag dikes which were
supplemented by pumping. As a result, little damage
occurred. However, flooding in downtown Reno was just
as extensive as in 1950 (Rigby and others, 1998), where a
strip one to two blocks wide on either side of the river from
Idlewild Park to the eastern city limits was flooded. However, the flood was well-forecast which allowed advanced
preparations and close coordination between agencies
which would engage in fighting the flood’s impacts. As a
result, flood damage in Reno was limited, with water
entering some basements and buildings downtown, and
with streets and lawns being buried in debris. However,
December 18–25, 1955. Like the November 1950 floods,
the December 1955 floods resulted from extremely heavy
rainfall combined with unseasonably warm temperatures
and melting of the Sierra Nevada snowpack. From December 21 through 24, total precipitation at the headwaters of
the principal river basins averaged from 10 to 13 inches
(Rigby and others, 1998), with an accompanying 15 inches
of snowmelt (USACE, 1970). At Woodfords, California,
an unbelievable 14.01 inches of rain fell in the six days
between the 18th and 23rd. According to NOAA Atlas 14:
Table 12. December 1955 flood flow data.
Station
Date
Peak or
Average Daily
Flow (cfs)
Event
Magnitude
Truckee River basin
Truckee
12/23/1955
7,760
25-year
Farad
12/23/1955
14,400
55-year
Reno
12/23/1955
20,800
50-year
12/24/1955
6,160
5-year
Wadsworth
(below Derby
Dam)
Carson River basin
Gardnerville
12/23/1955
17,600
90-year
Woodfords
12/23/1955
4,810
65-year
Carson City
12/24/1955
30,000
85-year
Ft. Churchill
12/26/1955
9,680
25-year
5,180
20-year
Walker River basin
Coleville
12/23/1955
60
caused "unexpected,” "disastrous,” and "catastrophic"
scouring and erosion of the riparian zone on the Truckee
River below Reno, especially in the Vista area (Horton,
1997b). The channel of Galena Creek was severely damaged, and two bridges over Steamboat Creek downstream
of the mouth of Galena Creek were destroyed. Also, about
1000 feet of U.S. Highway 395 was covered with debris,
and many roads in the Truckee Meadows were washed out
(USACE, 1972).
Without the water storage provided by Lake Tahoe,
Donner Lake, Boca, and especially Prosser Reservoirs, the
flooding downstream in Reno would have been much
worse. The newly constructed Prosser Creek Reservoir
began storing water on January 31 and accumulated 16,500
acre-feet during the flood. Rantz and Harris (1963) state:
"It is apparent that had Prosser Creek Reservoir not been in
operation, the flood peak of February 1 would have exceeded that of 1955 at Reno."
Total damage on the Truckee, Carson, and Walker
drainages was estimated at $4.4 million in 1963 dollars
(about $29.5 million in 2007 dollars) (Rantz and Harris,
1963). Approximately $3.25 million (about $21.8 million
in 2007 dollars) of this total was in Nevada, and most of
the damages in Nevada were on the Truckee Basin, due to
the urbanization in the Reno-Truckee Meadows area
(Rigby and others, 1998). Flooding on the Carson and
Walker Basins caused major damage to highways, irrigation systems, and ranch land. A total of approximately
32,100 acres were flooded in western Nevada. At the
request of Nevada Governor Grant Sawyer, the U.S.
Government declared seven western Nevada counties
disaster areas as a result of this flooding. These included
Churchill, Douglas, Lyon, Mineral, Ormsby (now Carson
City), Storey, and Washoe Counties (Rantz and Harris,
1963). Table 13 lists flood flow data for the JanuaryFebruary 1963 flood.
damage in Reno totaled only $900,000 (1955 dollars, about
$6.9 million in 2007 dollars), less than half the damage
which occurred in 1950. About $200,000 (1955 dollars,
about $1.5 million in 2007 dollars) in damage occurred in
Sparks (USACE, 1970). The Reno airport was flooded to a
depth of about 4 feet, stopping all air traffic for several
days. About 6000 acres were flooded in the Truckee
Meadows east of Reno and Sparks. As with the November
1950 flood, flows below Reno were much less due to the
backwater effect caused by the “Vista Reefs” which still
existed. However, this is what caused the Truckee Meadows to turn into a vast lake during major floods. Derby
Dam, located west of Wadsworth, was overtopped on
December 24, causing the dam to fail (Rigby and others,
1998). Table 12 lists flood flow data for the December
1955 flood.
January 29–February 2, 1963. As the result of 72 hours of
heavy rainfall from January 29 to February 1, 1963, widespread flooding occurred throughout central California and
western Nevada. Extensive flooding occurred in Reno,
with about 20 square blocks of the downtown area flooded
(Rantz and Harris, 1963), similar to the flooding which had
occurred in 1950 and 1955. Ten of the 12 bridges in Reno
were closed for an extended period (Rantz and Harris,
1963). South Virginia Street was flooded to a depth of 2
feet at Plumb Lane, and hundreds of homes throughout the
city were inundated (USACE, 1970). The deepening and
straightening work completed by the USACE in August
1962 on the Truckee River below Reno, especially the
removal of the Vista Reefs bedrock, helped drain the
Truckee Meadows more rapidly than in previous floods
(Horton, 1997b; USACE, 1980). However, this work also
Table 13. January–February 1963 flood flow data.
Station
Date
Peak or
Average Daily
Flow (cfs)
Event
Magnitude
February 12–21, 1986. As in all of the large previous floods
coming out of the eastern Sierra Nevada, the flooding in
February 1986 was caused by heavy rain with high snow
levels. However, snow levels during this event were somewhat lower than in the larger events, averaging between
7000 and 8000 feet. Snow levels were as high as 10,000 to
11,000 feet. Flood crests at higher locations (e.g. around
Lake Tahoe, Truckee River above Farad, West Fork Carson
River, and West Walker River) were higher during a second
1986 flood event which occurred March 7-10. Total damage
from this flood was estimated at $17 million, $11 million
of which was to public property. The estimate of damage
to private property and businesses was $6 million ($11.2
million in 2007 dollars). About 14,000 acres were flooded
in western Nevada (Rigby and others, 1998). Although
President Reagan declared five northern Nevada counties
disaster areas, Washoe County was hardest hit with about
$5 million ($9.4 million in 2007 dollars) damage to public
property, and about half of that amount was due to damage
to roads. Two known fatalities resulted from the flooding.
One Sparks man was swept away in flood waters while
removing furniture from his home. The other fatality was to
an elderly man who suffered a heart attack while shoveling
mud and debris from his home (Ekern, 1986).
Truckee River basin
Truckee
2/1/1963
11,000
45-year
Farad
2/1/1963
11,900
35-year
Reno
2/1/1963
18,400
40-year
Steamboat Cr. 1/31/1963
1,000
10-year
2/1/1963
18,900
40-year
2/1/1963
18,400
25-year
Vista
Wadsworth
(below Derby
Dam)
Carson River basin
Gardnerville
2/1/1963
13,400
45-year
Woodfords
2/1/1963
4,890
65-year
Carson City
2/1/1963
21,900
45-year
Ft. Churchill
2/2/1963
15,300
85-year
Walker River basin
Coleville
2/1/1963
2,870
5-year
Wabuska
2/3/1963
1,470
5-year
61
Table 14. February 1986 flood flow data.
Station
Date
Peak or
Average Daily
Flow (cfs)
Event
Magnitude
Lake Tahoe and Upper Truckee River basins
Upper Truckee R.
at S. Lake Tahoe
2/18/1986
1,740
7-year
Truckee River basin
Farad
2/18/1986
8,237
15-year
Reno
2/17/1986
14,400
25-year
Steamboat Cr.
2/17/1986
3,600
60-year
Vista
2/18/1986
16,100
30-year
Wadsworth (below
2/19/1986
16,900
25-year
Gardnerville
2/19/1986
7,380
10-year
Woodfords
2/19/1986
551
2-year
Derby Dam)
Carson River basin
Carson City
2/18/1986
13,200
20-year
Ft. Churchill
2/19/1986
16,600
100-year
Coleville
2/19/1986
1,290
2-year
Wabuska
2/21/1986
1,370
4-year
Walker River basin
62
floods in western Nevada and northern California
resulted from several moderate to heavy snowstorms in
the northern Sierra Nevada in December 1996, followed
by three subtropical, heavy rainstorms from the Pacific,
the last of which moved through the region from late
December 30, 1996 to early January 2, 1997. Warm
tropical-origin storms brought heavy rainfall and associated snowmelt to the region during the first few days of
January, which led to near-record to record rain-on-snow
flooding on most rivers and streams draining the east
slopes of the Sierra Nevada. The Walker, Carson,
Truckee, and Lake Tahoe basins received from three to
four times their normal precipitation for December 1996
and January 1997. Several locations within these basins
exceeded four or even five times their normal precipitation during these two months.
An estimated $1 billion in damage (1997 dollars,
$1.28 billion in 2007 dollars) occurred in the eastern
Sierra and western Nevada from flooding or its consequences, mostly during the first week of the month.
Two deaths were reported as a result of the flooding,
one in Washoe County and the other in Douglas
County. The death in Douglas County occurred in
Gardnerville on the evening of the January 2. A 59year-old man was swept into the east fork of the Carson
River while operating a front-end loader near its banks.
In Washoe County, the death occurred in Sparks on
January 3. A 53-year-old man was believed to have
Photo by Marilyn Newton. Photo courtesy of Reno Gazette-Journal
Flood damages from this flood were
highest on the Truckee River basin. However,
storage upstream of Truckee Meadows (Tahoe,
Prosser, Boca, and Stampede Dams) and
channelization through downtown Reno since
1970 prevented a major flood disaster. Also, the
fact that snow levels were somewhat lower than
in previous large floods helped to a large extent.
The most far-reaching impact was due to the
Truckee River severing a major natural gas
pipeline near Tracy, Nevada. This caused nearly
50,000 Southwest Gas customers in western
Nevada and eastern California to have to go
without heat for over a week after the flood.
Also, avalanches and mud, rock, and debris
flows caused closure of Interstate 80 up the
Truckee River canyon for almost three days.
Heavy snow and avalanches left the Mount Reno-Tahoe International Airport flooded, January 1997.
Rose Highway closed for nearly two weeks.
Runoff from Peavine Mountain into Lemmon Valley, north
fail. The flood washed out the Weeks bridge on U.S.
of Reno, threatened several homes and flooded the sewage
Highway 95A (Rigby and others, 1998). Table 14 lists
treatment plant there (Ekern, 1986). A landslide near Verdi
flood flow data for the February 1986 flood.
destroyed an old wooden water flume along the Truckee
December 29, 1996–January 16, 1997. The flooding of
River. Due to the rapidly rising water nearly all of the
January 1997 will long be remembered as one of the most
bridges over the Truckee River in Reno had to be closed, the
significant and devastating flood events in recorded history
exceptions were the Wells and Keystone Avenue bridges.
on the Walker, Carson, Tahoe, Truckee, and Susan River
Serious flood damage was also reported in the Carson
basins. An estimated 63,800 acres were flooded in western
Valley. The Cradlebaugh Bridge on U.S. 395 over the
Nevada (Rigby and others, 1998). The precipitation reCarson River was closed. About 200 residents below El
ceived during the two-month period of December 1996Dorado Canyon Dam near Dayton were evacuated as
January 1997 was of near-record to record proportions,
emergency officials were concerned that the dam might
especially in the eastern Sierra Nevada. The New Year's
Photo courtesy of Nevada Department of Transportation
been swept into the Truckee River. He apparently went to
his place of business in order to retrieve some personal
belongings. The road to his business was washed away,
and it was surmised that he and his truck were swept into
the Truckee. According to the Red Cross, an estimated 52
injuries occurred across the eastern Sierra and western
Nevada, with four persons requiring hospitalization.
Flooding on the Truckee River destroyed or severely
damaged many homes, businesses, warehouses, and roads
in Placer County, California (including Tahoe City); in
Nevada County, California (including the town of
Truckee); in Washoe County, Nevada (including Reno,
Sparks, Lockwood, Wadsworth, and Nixon), and in Storey
County, Nevada (including Lockwood and Mustang). The
airport in Reno was closed due to flooding for nearly two
days. Interstate 80 running both east and west of Reno was
closed for a similar period, as was U.S. Highway 395
which leads north and south. The Truckee Meadows
became a lake estimated to cover an area of 3,830 acres.
Catastrophic flows on the lower Truckee River were
only prevented by the judicious and timely regulation of
upstream reservoirs by the Federal Water Master. These
reservoirs include Stampede and Boca Dams on the Little
Truckee River, Prosser Dam on Prosser Creek, and Martis
Dam on Martis Creek. Only Boca Dam was available for
such flood prevention purposes in 1950 or 1955. However,
if ample storage had not been available in these reservoirs,
the 1997 flood event would have been far worse and would
have been the record flood.
Side of Helms gravel pit in Sparks being washed away
beneath westbound lanes of Interstate 80 during the
January 1997 floods.
On the East Fork, West Fork, and mainstem of the
Carson River the January 1997 floods were the worst of
record by all accounts: the highest stages, flows, and
damages of record. The flooding destroyed or severely
damaged many homes and businesses in Alpine County,
California (including the towns of Woodfords and Markleeville); Douglas County, Nevada (including Minden,
Gardnerville and Genoa); Carson City County, Nevada;
and Lyon County, Nevada (including the towns of Dayton
and Weeks).
The January 1997 flooding was also the worst of
record on the East, West, and upper mainstem (above
Yerington) Walker Rivers. Extensive flooding on
Table 15. December 1996–January 1997 flood flow data.
these rivers caused massive destruction in Mono
County, California (especially in Walker, Coleville,
Peak or
Event
Topaz, and Bridgeport) and in Lyon County, Nevada
Average
Daily
Station
Date
Magnitude
Flow (cfs)
(including Smith, Wellington, Mason, and Yerington).
In addition to the flooding, some mountain areas
Lake Tahoe and Upper Truckee River basins
experienced extensive mud slides and debris flows
Upper Truckee R.
which closed major arterial highways into the Lake
1/2/1997
5,480
75-year
at S. Lake Tahoe
Tahoe region. The floods also washed out several
Truckee River basin
river gages along the three main western rivers (the
Walker, Carson, and Truckee), making warnings and
Truckee
1/2/1997
11,900
50-year
forecasts much more difficult. The river gage on the
Farad
1/2/1997
14,900
60-year
West Fork Carson River at Woodfords, California was
Reno
1/2/1997
18,200
40-year
left high and dry when the flood caused the river to
reroute itself several yards away. The river gage was
Steamboat Cr.
1/1/1997
2,090
25-year
soon established at a new location by the USGS. All
Vista
1/2/1997
18,500
40-year
other damaged river gages were repaired or replaced
Wadsworth (below
1/3/1997
19,700
30-year
by the USGS. Table 15 lists flood flow data for the
Derby Dam)
December 1996–January 1997 flood.
Carson River basin
Gardnerville
1/3/1997
20,300
150-year
Woodfords
1/1/1997
8,100
300-year
Carson City
1/3/1997
30,500
90-year
Ft. Churchill
1/3/1997
22,300
250-year
Coleville
1/2/1997
12,300
500-year
Wabuska
1/6/1997
2,600
10-year
Walker River basin
63
December 30, 2005–January 1, 2006. Rainfall from a
series of late December storms caused flooding
throughout far western Nevada and the northern and
central Sierra. Up to 6 inches of rain fell in the Reno
and Carson City areas on December 30th and 31st,
with up to 9 inches in the Sierra foothill areas (below
about 6000 feet) near these cities. Six to 11 inches of
rain fell in the Lake Tahoe basin and along the Sierra
crest. The very heavy rain in the Sierra foothills and in
the Lake Tahoe Basin was very unusual, and caused
Photo by Heather Angeloff
significant flooding on many small creeks and streams
draining the eastern Sierra. Several had record to near
record flooding.
Soils were already saturated from storms that occurred earlier in December. Streams and rivers remained
high during the last week of the month when another wet
storm brought more precipitation from the 26th through the
28th. The storms that occurred from the 26th through the
28th deposited up to 3 inches of precipitation in the Sierra
Nevada. Although precipitation totals were less than the
previous storm and snow levels were lower, this storm
caused large amounts of runoff because soils were still
saturated from the storm that ended on the 23rd. This storm
caused creeks, streams, and rivers to rise nearly to the
levels reached on the 22nd, and again completely saturated
all eastern Sierra Nevada and western Nevada watersheds.
Rivers and streams receded very slowly and it was apparent on the 28th that any additional rainfall would quickly
run off. The most intense storm of the month moved into
the Sierra on the 30th. The flooding that occurred was
mainly from a “short duration heavy rainfall event with
only minor contribution from snow melt” (Wallmann and
others, 2006). This was a warm storm with snow levels at
almost 10,000 feet.
In Washoe County, damage was reported at over 900
businesses in the Sparks industrial area. A levee along
Steamboat Creek failed and caused the University of
Nevada, Reno agricultural farm in east Reno to flood.
Flooding in Lemmon Valley, north of Reno, December 2005.
Around 1,800 animals were evacuated to higher ground,
but 344 sheep died in the floodwaters. Figure 28 compares
the areas that were flooded during the December 2005January 2006 flood with those areas that were flooded
during January 1997. Significant flood damage also occurred to homes, businesses, and public infrastructure in
Carson City, Storey, Lyon, and Douglas Counties, all of
which were declared Federal Disaster Areas. Preliminary
total damage to public property in western Nevada was
estimated at $16.1 million by the Federal Emergency
Table 16. December 2005–January 2006 flood flow data.
Management Agency. California counties along the
eastern Sierra also suffered significant flood damPeak or
ages, with preliminary estimated losses to public
Event
Average Daily
Station
Date
Magnitude
infrastructure at over $15 million. Table 16 lists
Flow (cfs)
flood flow data for the December 2005–January 2006
Lake Tahoe and Upper Truckee River basins
flood.
Upper Truckee R.
at S. Lake Tahoe 12/31/2005
2,850
15-year
Truckee River basin
Truckee
12/31/2005
6,030
15-year
Farad
12/31/2005
10,100
20-year
Reno
12/31/2005
16,400
30-year
Steamboat Cr.
12/31/2005
3,600
60-year
Vista
12/31/2005
13,700
20-year
Wadsworth (below 12/31/2005
Derby Dam)
14,900
20-year
Carson River basin
Gardnerville
12/31/2005
9,730
20-year
Woodfords
12/31/2005
2,720
15-year
Carson City
12/31/2005
11,900
15-year
Ft. Churchill
1/2/2006
9,800
25-year
12/31/2005
1,805
2-year
1/2/2006
662
2-year
Walker River basin
Coleville
Wabuska
64
FLASH FLOODS
During the warmer half of the year (April through
September), very little precipitation occurs over
western Nevada and the eastern Sierra Nevada.
However, the rain that falls during summer thunderstorms can be very intense and can occur during a
very short period of time. Due to the intensity of
these brief showers the rain that makes it to the
surface (the rain that does not evaporate on its descent) does not have time to soak into the hard dry
ground. This rainfall runs off and can produce damaging flash floods. A dry river bed can quickly
become a raging river if one of these rain showers is
overhead.
Flash floods can occur at any time of the year but are
most common during the period from April through
September. During late-summer subtropical moisture is
brought into the region from the Pacific Ocean and the
Gulf of Mexico. This is the summer monsoon and
during its height in July and August large amounts of
moismoisture can provide fuel for afternoon thunderstorms. It is these thunderstorms that can cause some of
the most intense flash floods.
Flash floods can be very destructive. The water in the
Figure 28. Map comparing the areas flooded during the December 2005–January 2006 flood with those areas
flooded during the January 1997 flood.
July 18–27, 1913. Rainfall was reported every one of these
days at Reno. Almost an inch of rain (0.91 inch) fell on
July 23. The worst damage occurred west of Reno. With so
much water flowing out of Galena and Browns Creeks,
Pleasant Valley was described as a solid sheet of water.
Flood debris covered parts of the Reno-Carson City road
(now U.S. Highway 395). A stranded automobile was
covered with 25 to 30 feet of debris. Ranch buildings and
fences were flooded or destroyed in Pleasant Valley.
flash flood can combine with debris such as mud, sand,
rocks, and boulders and can cause tremendous damage.
Hoyt and Langbein (1955) stated that it “is not unusual for
a mudflow to contain about as much solid matter as water.” Roads can be blocked or even washed away.
Topography can be extremely important in producing
flash floods. Steep slopes can provide the focus for thunderstorm formation, and they can then channel the resulting rainfall swiftly down into the surrounding lowlands
(Dietrich, 1979). Flash floods are usually confined to a
relatively small area and rarely contribute to mainstem
river flooding. Some of the largest and most damaging
flash floods which occurred in the region are listed below.
June 11, 1927. Torrential rains caused major damage
southwest of Reno during the late-afternoon and evening
of June 11. Rainfall rates of over 2 inches per hour near the
headwaters of Browns Creek caused the Grass Lake
Irrigation Reservoir to fail. The resulting flash flood
washed out the Mt. Rose Highway just below the dam on
Browns Creek. The flash flood killed livestock, flooded the
Reno-Carson City highway (now U.S. Highway 395),
washed out two bridges, destroyed a house, and flooded
ranch buildings and irrigation ditches. The flash flood also
washed out over 1000 feet of the Virginia and Truckee
Railroad in Pleasant Valley. The heavy rainfall was isolated however. Reno only reported 0.07 inches of rain for
the entire day.
July 13–18, 1911. Stormy weather occurred in mid July
1911 with thunderstorms being reported each day from
July 12 through 19. Heavy rain fell on the 13th with 0.46
inches of precipitation recorded at Reno. Landslides
destroyed almost a mile of the Southern Pacific Railroad
tracks near Floriston, California. On the new road extending from Reno to Lake Tahoe (the current Mt. Rose Highway) a bridge was washed out over Galena Creek during
this flash flood.
65
Photo courtesy of the Nevada Historical Society
July 20, 1956. A wall of water reported to be 10 feet high
on Galena Creek washed several automobiles off of Mount
Rose Highway. Four persons drowned in the flood waters.
Farther north this same storm dumped heavy rain on
Peavine Mountain, causing the worst flood ever seen on the
mountain’s south slopes. The flash flood descended the
side of the mountain and destroyed homes and flooded
streets in northwest Reno. Businesses were also flooded in
the northwest section of downtown. This same area of
northwest Reno was flooded by a flash flood the previous
July on creeks which were fire-denuded and overgrazed.
August 11–19, 1965. Strong thunderstorms over the Sierra
Nevada and Lake Tahoe basin caused extensive flash
flooding. The heaviest rainfall was on the 15th and 16th
around South Lake Tahoe. Mt. Rose Highway was washed
out and was closed for three days. Due to the prolonged
heavy rainfall Lake Tahoe experienced its latest recorded
crest and the gates of the Lake Tahoe Dam at Tahoe City
had to be opened to keep the lake level below the legal
limit. A mud slide 300 feet wide closed U.S. Highway 395
in Pleasant Valley for three hours. Approximately a mile
upstream of Floriston, California, the Southern Pacific
Railroad Bridge over Gray Creek was washed out. Large
amounts of sediment and debris were introduced into the
Truckee River from Gray and Bronco Creeks. Because of
this, the cities of Reno and Sparks could not draw water
from the Truckee until August 19, and this was only after
the Truckee River was diluted by water released from Lake
Tahoe and Boca Reservoir.
Damage in northwest Reno that resulted from the
Peavine Mountain flash flood on July 20, 1956.
mud and debris. The landslide-induced flooding caused over
$2 million in damages (Glancy and Bell, 2000). It was
fortunate that the debris slide did not spill into drainages just
a mile to the north (where Davis Creek County Park is
located) or to the south (where Bowers Mansion County
Park is), since both of these parks were very crowded with
visitors, due to the Memorial Day holiday.
March 10, 1995. Very heavy rainfall of around one-half
inch per hour occurred between 4 pm and 6 pm on March
10, 1995. Moderate rainfall had continued most of the day
from around 10 a.m. to 10 p.m. with rainfall totals of
between 1 inch and 3.5 inches. The heavy rainfall during
the evening, combined with saturated soil and snowmelt,
caused a flash flood on Long Valley Creek in Storey
County. The Rainbow Bend subdivision was flooded and
three bridges over the creek were washed out (including
the main access road to the subdivision). With the water
main and other utilities impaired, the subdivision was
evacuated, and over $2.5 million in damage resulted.
May 29–30, 1983. Very rapid melting of a near-record to
record snowpack caused many mudslides and flash flooding throughout the eastern Sierra. Two very damaging flash
floods are extremely noteworthy. The first occurred around
5:00 am on May 29. On the northwest side of Squaw Valley
a 200-foot-wide mile-long mudslide roared down Silver
Peak Slope. Over a dozen expensive homes sustained
damage, with five of them suffering serious damage.
The next day one of the largest flash floods in the area’s
history occurred. Around noon on May 30 a huge mudslide
started as a 15-acre area at around 8000 feet came loose and
slid down the very steep south face of Slide Mountain. This
debris spilled into and completely filled Upper Price Lake
on Ophir Creek. The water from Upper Price Lake then
spilled into Lower Price Lake and then, in a matter of
minutes, sent a 15- to 20-foot wall of water, mud, and
boulders down Ophir Creek into Washoe Valley and then
into Washoe Lake. Traveling at 40 mph the flash flood
destroyed everything in its path. One person was killed and
four people were injured. Four houses were completely
destroyed, and five others were damaged. The flash flood
washed out Nevada Highway 429 (old Highway 395) where
it crosses Ophir Creek. U.S. Highway 395 was closed
because over 600 yards of the highway were covered by
Jan. 1–3, 1997. Extremely heavy rainfall, combined with
complete melt-off of heavy low-elevation snow cover,
caused moderate to severe flash flooding throughout the
Lake Tahoe basin, and on streams coming out of the Sierra
Nevada and the Virginia Range in the Truckee River basin.
Incredibly extensive damage resulted, separate from the
huge losses due to the mainstem flooding.
June 20–21, 2002. Torrential rainfall produced flash
flooding during the evening on both June 20 and 21 in the
Spanish Springs area northeast of Reno. Strong thunderstorms produced hail and almost an inch of rain in less than
one hour the evening of the 20th. The very next evening
strong thunderstorms again formed over the area. An estimated 3 inches of rain fell in about one hour. The runoff,
combined with sediment and debris, caused extensive
damage. Damage to the area was estimated at over $1
million. Especially hard hit was the new Spanish Springs
High School, which suffered over $500,000 damage.
66
FLOOD FREQUENCY IN THE TRUCKEE, CARSON,
AND WALKER RIVER BASINS
Flood frequency is an estimated measure of how often a
particular flood severity may be expected on a river. This
information is derived from data from as many past floods
as possible (assuming the basin is relatively unchanged
during the period) using various statistical methods which
are beyond the scope of this report. Flood frequencies for
some river gage locations on the Truckee, Carson, and
Walker river basins are listed in Table 17. The USGS offices in Carson City, Nevada and Sacramento, California
estimated the flood frequencies for all stations using Bulletin 17B, Guidelines for determining flood flow frequency
(USGS, 1982). Where flow data are available, the frequency of that magnitude of flow is best expressed as the
percent probability that greater than a particular flow will
occur in any given year (e.g., "Greater than X cfs has a ten
percent chance of occurrence during any year."). However,
it is usually expressed as an “X-year flood event”, for example, a “100-year flood event,” by tradition. This does
not mean that an X-year flood will happen, on average,
every X years. The correct definition of an “X-year flood
event” is “the magnitude of a flood which has a 1-in-X
chance of being equaled or exceeded in any future oneyear period, given our current knowledge of what has
happened in the past.” So, for example, a 100-year flood
has a one in 100 (1%) chance of being equaled or exceeded
in any one year, a 10-year flood a 1 in 10 (10%) chance, a
2-year flood a one in 2 (50%) chance, etc.
Table 17. Peak flow (cubic feet per second) probabilities for the Truckee, Carson, and Walker river basin stations.
Frequency (annual probability %)
Station
USGS #
2-year
(50%)
10-year
(10%)
25-year
(4%)
50-year
(2%)
100-year
(1%)
10336610
740
2,250
3,510
4,720
6,200
Lake Tahoe and Upper Truckee River basins
Upper Truckee River at South Lake Tahoe
Truckee River basin
Truckee River near Truckee, CA
10338000
1,170
4,590
8,210
12,260
17,870
Truckee River at Farad, CA
10346000
2,750
7,550
11,020
14,100
17,660
Truckee River at Reno, NV
10348000
2,770
9,590
15,300
20,800
27,500
Galena Creek at Galena Creek State Park, NV
10348850
60
460
1,310
2,840
6,100
Steamboat Creek at Steamboat, NV
10349300
140
950
2,010
3,300
5,200
Truckee River at Vista, NV
10350000
3,060
9,900
15,520
20,830
27,240
Wadsworth, NV (below Derby Dam)
10351600
2,344
10,800
18,050
24,900
32,960
Carson River basin
East Fork Carson River near Markleeville, CA
10308200
2,520
8,580
14,000
19,400
26,000
East Fork Carson River near Gardnerville, NV
10309000
2,500
6,900
10,500
14,000
18,280
West Fork Carson River at Woodfords, CA
10310000
800
2,200
3,330
4,435
5,790
Carson River near Carson City, NV
10311000
2,440
9,230
15,900
23,030
32,490
Carson River near Ft. Churchill, NV
10312000
2,070
6,440
9,815
12,900
16,540
Carson River below Lahontan Reservoir near
Fallon, NV
10312150
1,530
2,430
2,950
3,380
3,840
Carson River at Tarzyn Road below Fallon, NV
10312275
145
930
1,890
3,020
4,610
East Walker River near Bridgeport, CA
10293000
450
1,040
1,450
1,810
2,210
West Walker River below Little Walker River
near Coleville, CA
10296000
1,850
4,000
5,480
6,760
8,220
West Walker River at Hoye Bridge near
Wellington, NV
10297500
930
2,450
3,860
5,330
7,260
Walker River near Wabuska, NV
10301500
620
2,500
4,045
5,465
7,120
Walker River basin
All data are from the USGS.
67
Photo by Tom Roseberry
Downtown Reno during the flood of January 1997. View down Truckee River showing Sierra Street, Virginia
Street, and Center Street bridges.
The Top 25 Weather-Related Events in the Region Since 1850
by Brian F. O’Hara
during periods of flooding. Rapid snowmelt can quickly
cause rivers and streams to overflow their banks, and these
problems can be exacerbated if the snowmelt is caused by or
accompanied by heavy prolonged rainfall.
Listed below are the 25 weather-related events that
have caused the most problems for residents of western
Nevada and the eastern Sierra since weather records started
to be kept in the mid nineteenth century. It should not be
surprising that four of the top 10 events are major floods.
Flooding can cause problems on spatial and temporal
scales that are not easily matched by other extreme weather
events. High winds can cause damage across an area but
not all residents may be affected, and the high winds may
last only a few hours. A winter storm may bring strong
winds and heavy snowfall, but the storm usually moves out
of a region after 24 to 36 hours. Roads and sidewalks may
be clear of snow by the next day. The very cold air associated with the snowstorm, however, may remain over a
region for up to a week after the storm has passed.
A major flood is different in that the flood waters can
completely inundate an area of tens of square miles. The
effects are not isolated as in some thunderstorm or high
wind events. All areas below the top of the flood water are
Western Nevada and the Lake Tahoe area experience
interesting weather each year. Thunderstorms mainly occur
during the warmer half of the year, but are more numerous
during some summers than during others. Tornadoes and
hail are relatively rare, but gusty winds and lightning
associated with thunderstorms occur more frequently.
Wildfires, whether caused by lightning or humans, can be a
tremendous danger from late spring into mid autumn. Dry
plants provide fuel for the wildfires, and hot, dry weather
conditions can keep wildfires burning for weeks at a time,
sometimes threatening homes and entire communities.
Significant events also occur during the colder half of
the year. Strong winds associated with intense low pressure
systems coming in off the Pacific Ocean can cause damage
throughout the region. Snowstorms can deposit large
amounts of snow and hamper travel for days at a time. The
frigid air masses that often accompany these snowstorms
can cause dangerously cold temperatures. These cold
temperatures, as reflected in extremely low wind-chill
indices, can be life-threatening if people are caught outdoors unprepared. Low temperatures can also cause additional problems ranging from frozen pipes to overburdened
public utilities. Perhaps the most significant problems occur
68
directly affected. Residential and business areas can
become isolated. Those areas in the flood zone are often
completely cut off, and the flood waters can remain over an
area for days at a time. Roads and sidewalks cannot be
cleared of flood waters as they can be cleared of snow
cover after a snowstorm. Property in contact with the flood
water becomes increasingly damaged. As a result, damage
associated with the flood event can cost upwards of $10
million, and oftentimes much more than this. These are
some of the reasons why a flood can affect a community
much more severely than other weather events might.
Among the 25 most significant weather events listed
below, winter storms with their heavy snowfall, cold
temperatures, and high winds are well represented. However, some of the most significant weather events listed
involve major floods. In fact, the most significant event,
the January 1997 floods, can certainly be considered one of
the major events (weather-related or otherwise) that has
affected the region during the last 150 years.
debris down Ophir Creek, through Washoe Valley, and into
Washoe Lake, all in a matter of minutes. The debris flow
washed out Nevada Highway 429 and closed U.S. Highway 395.
21. Waterfall Fire in late July 2004. This human-caused
fire burned homes in the foothills west of Carson City. At
its height it threatened to spread into Carson City itself, and
possibly endangering the capitol and much of downtown.
Fortunately, the wildfire was contained before that happened.
20. December 2002 high wind event. Strong synoptic-scale
winds caused damage throughout northeast California and
western Nevada on December 14. The Reno and Carson
City areas suffered extensive damage as the high winds
tore roofs off of buildings, blew down fences and signs,
and toppled trees. Total damage throughout the area was
estimated at almost $10 million.
19. February 16–20, 1990 snowstorm and cold outbreak.
Another impressive February snowstorm in the Truckee
Meadows but with a colder air mass than the one associated with the February 1959 snowstorm mentioned above.
A total of 21.1 inches of snow fell with this storm from
February 16–18 at Reno. An incredible 18.0 inches fell just
on the 16th. Very cold air filtered into the region with
average daily temperatures almost 30° below normal. At
Reno the morning low was only 2º above zero on the 18th,
and dropped to -7º on the 19th and -6º on the 20th. Due to
the very cold temperatures, deep snowcover stayed around
for a longer period than in February 1959. Thirteen inches
of snow was on the ground at Reno on the 17th. At least 10
inches of snow cover was reported at the Reno airport
through the 21st.
25. Snowstorm of early December 1919. A snowstorm
during the first five days of December 1919 dumped
almost 3 feet of snow on Reno. From December 1 through
the 5, a total of 33.6 inches of snow was reported. This was
all but 0.2 inches of the month’s total of 33.8 inches. A
total of 10.6 inches of snow fell on December 2 and 11.5
inches fell the next day. By the evening of December 5
there was 18 inches of snow on the ground.
24. Record high temperatures in July 2002. This turned
out to be the fourth warmest July on record at Reno
(behind the Julys of 2003, 2005, 2006). The average
temperature for the month was 78.4º. The temperature
reached 100º on six days. On both July 10 and 11 the high
temperature was 108º, setting an all-time record for Reno.
At Carson City the high on the 10th was 105º and on the
11th it reached 104º. The 105º on the 10th is the all-time
record high for Carson City. It was around 90º on these
dates at Tahoe City.
18. Warm summer of 2003. This was the warmest summer
on record at Reno until the summer of 2006. The months of
June, July, and September were the warmest June, July,
and September on record, and August was the fifth warmest August on record (until the next two years, when
August 2004 became tied for the third warmest August on
record, dropping August 2003 to sixth place, and then
August 2005 became the second warmest August ever,
dropping August 2003 to seventh place). With an average
temperature of 79.2º July 2003 was the warmest month
ever in Reno (a record which stood until the very warm
July 2005 when the average temperature for that month
was 80.0O). The temperature reached 100º or more on nine
days in July at Reno. At Carson City the high temperature
on five of those days in July set the record for those dates.
23. February 10–12, 1959 snowstorm and cold outbreak.
This was an impressive snowstorm during the second week
of February 1959. A total of 21.9 inches of snow fell
during the three-day period of February 10–12 at Reno. By
the 12th a foot of snow covered the ground at Reno. During
the three days from February 11–13, a total of 13.9 inches
of snow fell at Carson City. The cold air mass, combined
with the deep snow cover, helped daily average temperatures drop to almost 25° below normal. Temperatures
dropped into the single digits with morning lows of 5°, 3°,
and 8° above zero being reported on February 12th, 13th,
and 14th, respectively at Reno. Warmer air returned to the
region by the 16th and the snow cover quickly melted.
17. Carson City fire in late September 1926. A wildfire in
Clear Creek Canyon south of Carson City destroyed
ranches and forest between Carson City and Lake Tahoe.
Erratic winds made this fire difficult to control but firefighters kept the fire from entering Carson City. Five men
were killed when they were trapped by the fire in a gully in
Clear Creek Canyon.
22. Washoe Valley debris flow in May 1983. A 15-acre
area on the south side of Slide Mountain slid into Upper
Price Lake on Ophir Creek, completely filling the lake.
Water spilling out of Upper Price Lake entered Lower
Price Lake and sent a 15- to 20-foot wall of water and
69
16. Winter of 1951–1952. This was a severe winter with
deep snow and cold temperatures in the Sierra. Heavy
snow fell in western Nevada in January and again in
March. On March 20 there was 166 inches (13.8 feet) of
snow on the ground at Tahoe City (the most in its history).
road to choose Lake’s Crossing as their Truckee Meadows
site instead of Glendale to the east. As a result, this helped
Reno eventually surpass Carson City in population and
become the major city in the region.
10. January 14–15, 1988 high wind event. Extremely high
winds were reported across western Nevada as a strong
cold front moved through the region the night of January
14–15, 1988. A wind gust of 90 mph was reported at the
Reno airport. As stated in Storm Data, the “greatest wind
speed reported was 106 mph in southwest Reno.” (USDC,
1988). The entry in Storm Data listed the various types of
damage that resulted, such as uprooted trees, damaged
fences, downed power lines, and broken windows. A roof
was torn off of a house in southwest Reno. An estimated
$160,000 in damage resulted when a chapel steeple fell
through the roof of a high school classroom. Hangars and
private planes were damaged at both the Reno and Stead
airports. Damage at Stead Airport alone was estimated at
between $500,000 and $600,000. Approximately 15,000
residences lost power.
15. March 1907 flood. This flood from March 16 to 23
was caused by heavy rain falling on deep snowcover.
Extensive damage occurred throughout the Truckee and
Carson River basins.
14. February 3–8, 1989 snowstorm and cold outbreak.
Incredibly cold temperatures visited the region during early
February 1989. As with the December 1972 storm
(mentioned below), snowfall totals were not huge. A total
of 9.8 inches of snow fell over the three-day period from
February 3 to 5 at Reno. An extremely cold air mass
descended over the region with daily temperature averages
almost 40° colder than normal. On February 5 the temperature dropped to -10º. The morning low was below zero the
next three days with readings of -15º, -16º, and -12º being
reported on February 6, 7, and 8, respectively. These low
temperatures from the 5th through the 8th remain the record
lows for these dates in Reno. The -16º recorded on the 7th is
the lowest temperature ever recorded in February in Reno.
9. January 1916 snowstorms. With a total of 65.7 inches
of snow, January 1916 is the snowiest month on record at
Reno. Four separate snowstorms moved through the region
during the month. During the first storm, from January 1 to
5, a total of 10.2 inches of snow fell at Reno. At Tahoe
City 31.0 inches of snow fell on January 3 alone. Another
13.8 inches of snow fell at Reno from the 8th through the
10th. The biggest snowstorm of the month (and one of the
major snowstorms in Reno’s history) occurred on January
17–18. On the 17th a record 22.5 inches of snow fell, more
snow than on any other day in Reno’s history. On the 18th
another 3.0 inches of snow fell, giving a storm total of 25.5
inches. The fourth and final snowstorm of the month
occurred from the 27th through the 30th with 14.7 inches of
snow being reported at Reno.
13. Winter of 1948–1949. Extremely cold temperatures
visited the region during the depth of winter. For ten days,
from January 23 through February 1, 1949 the morning low
dropped to zero or lower each day at Reno. The entire
month of January was cold. For 20 days (January 14
through February 2) the morning low dropped to 10º or
lower. For 33 consecutive days (January 2 through February 3) the low temperature each morning at Reno was 20º
or lower. At Carson City, the -20º reading the morning of
January 26 remains its record low for January.
12. Late December 2004 – early January 2005 snowstorms. A pair of snowstorms in late December 2004 and
early January 2005 deposited up to 2 feet of snow in the
Reno and Carson City areas. Over 3 feet of snow fell in the
foothills along the east slopes of the Carson Range. This
was the most snowfall that the region had seen since the
record-setting snowfall experienced during January 1916.
Traffic was paralyzed for days with some side streets not
being cleared for two weeks. Fortunately temperatures
remained near normal with nighttime lows dropping only
into the lower 20s or upper teens during most of the period.
Even with close to 20 inches of snow on the ground in mid
January, morning lows fell into the single digits on only
two days in Reno (the morning low was 6º on the 13th and
8º on the 14th).
8. February 1986 flood. Heavy rainfall contributed to
significant flooding over western Nevada and the eastern
Sierra in mid February 1986. Two persons died as a result
of the flood. The Truckee River basin was the main basin
affected. Water storage upstream at Stampede Reservoir,
combined with channelization in downtown Reno
(completed during the previous 15 years), prevented even
greater damage.
7. December 4–11, 1972 snowstorm and cold outbreak. An
extremely cold air mass accompanied this snowstorm in
early December 1972. Snowfall totals were not overly
impressive with 4.8 inches of snow falling on December 4
and an additional 3.1 inches of snowfall being reported at
the Reno airport two days later. However, the very cold air
mass that settled over the region was almost unprecedented.
Temperatures quickly dropped after the snowstorm
moved through. The average daily temperature at Reno on
December 8 was almost 30° below normal, with a morning
low of -12º, and conditions only grew worse. The morning low
temperature readings were below zero for the next five days.
11. Late December 1867 – early January 1868 flood. This
flooding destroyed all of the bridges in the Eagle and
Carson Valleys. In the Truckee Meadows bridges at Lake’s
Crossing (now Reno) and Glendale (east of present-day
Sparks) were also destroyed. The extensive flooding
throughout the region convinced the Central Pacific Rail70
On two of these days the temperature didn’t even climb out
of the single digits. The afternoon high on December 9 at
Reno was only 6º above zero, and the high on the 11th was
9 above. From the 9th through the 11th the average daily
temperatures were more than 30° below normal. The low
temperatures on the six days from December 8–13 were 12º, -16º, -11º, -15º, -2º, and -2º, respectively. The low
temperatures for the four-day period from the 8th through
the 11th remain the record lows for these dates at Reno. The
-16º recorded on the 9th is still the official record low for
the entire month of December at Reno.
this flood than during the flood of 1950. However, flood
mitigation and other preparations during the previous five
years helped to decrease the potential damage. But the
floodwaters covered almost 100,000 acres and affected the
Truckee, Carson, and Walker River basins.
2. Late November to early December 1950 flood. This
flood was the most severe to affect the region since streamflow records started to be kept in the 1890s. Like many
previous floods, this one was caused by heavy rainfall
combining with snowmelt from higher elevations. Soils
were already saturated from precipitation received earlier
in the month, and this contributed to the rapid flooding.
Major damage occurred in the Truckee, Carson, and
Walker river basins. Reno experienced major damage. All
bridges across the Truckee in downtown Reno were closed,
with the Rock Street bridge being destroyed. Water was 3
feet deep in much of downtown Reno. Farther south, two
new bridges over the Carson River between Carson City
and Minden were overtopped, and the Lloyd Bridge southeast of the Nevada State Prison near Carson City was
nearly destroyed.
6. Winter of 1889–1890. This was a very cold and snowy
winter across the Sierra and western Nevada. The lowest
temperature ever recorded at Reno occurred on January 8
when the nighttime temperature bottomed out at -19°F. The
temperature fell to -18° on both January 7 and 9. Reports of
low temperatures in Carson City ranged from -22° to -27°
on January 8 and 9. A total of 31.4 inches of snow fell in
Carson City in December, 55.1 inches fell in January, and
another 26.9 inches of snow fell in February.
5. Virginia City fire in late October 1875. This fire, driven
by strong winds, destroyed Virginia City, at the time the
largest city in Nevada. Two persons died and hundreds
were left homeless. The mines north of the city were saved,
although some mine buildings were lost. The town and
mine buildings were reconstructed, but Virginia City had
seen its best days. Whether due to the fire or not, Virginia
City declined in importance during the next decade.
1. January 1997 flood. This is perhaps the major weatherrelated event in the region’s history. The precipitation that
fell during December 1996 and January 1997 was of nearrecord to record amounts, especially in the eastern Sierra.
River basins throughout the eastern Sierra and western
Nevada were affected, from the Susan River in the north to
the Walker River in the south.
A major winter storm dropped near-record heavy snow
in the Sierra and western Nevada in mid December. A
warmer system then brought rain to the region. With snow
levels as high as 12,000 feet, rain melted much of the snow
cover in the foothills of the Carson Range and Sierra Nevada, and across western Nevada. Mudslides caused much
damage in the Lake Tahoe basin. Hundreds of homes and
businesses were damaged. The flooding caused the surface
of Lake Tahoe to rise to its highest level since 1917.
Damage was catastrophic in the Reno and Carson City
areas. This was mainly because the area was so built up with
businesses and residential areas. The Reno/Tahoe International Airport was forced to close for a day and a half. Many
casinos in downtown Reno also had to close. Two deaths
and numerous injuries resulted from this major flood.
4. Drought of 1986–94. This was a severe drought, rivaling
the prolonged drought of the late 1920s and 1930s. This
drought, however, occurred during a period of rapid growth
in the Reno, Carson City, and Lake Tahoe region. The lack
of precipitation, combined with the population increase,
exacerbated growth problems experienced by the region
during this period. Washoe Lake was completely dry in the
summer of 1989 and again in 1991, the first such occurrences since 1934.
3. Late December 1955 flood. The flooding that occurred
during late December 1955 resulted from extremely heavy
rainfall. Precipitation at the headwaters in the eastern
Sierra averaged over 10 inches, with 15 inches of water
being supplied from snowmelt. Flooding was worse during
71
Acknowledgments
by Brian F. O’Hara
Significant weather events for the region were collected and analyzed using information in the publication
Storm Data (USDC, 1959–2005). Significant events were
also inferred from the LCDs for Reno. The software program XMClimate proved to be a good comparison to
information and conclusions that we derived from manual
research. Information about weather events and climatic
conditions in rural areas of the region were derived from
cooperative weather reports. Cooperative weather observers have been supplying climatological data to the U.S.
Weather Bureau and National Weather Service for over
100 years. Their dedicated, selfless service (oftentimes
provided by individuals free of charge over periods of
decades) has provided an invaluable source of data to the
nation to supplement official Weather Bureau and National
Weather Service weather and climate observations.
Additional information about specific weather events
was gathered from newspapers and other publications
archived by the Nevada Historical Society in Reno, the
Getchell Library at the University of Nevada in Reno, and
the Washoe County Public Library in Reno. The staff at the
Nevada Historical Society was tireless in their assistance to
us. Especially worthy of appreciation are librarian Michael
Maher and librarian-assistant Marta Gonzalez-Collins.
Their extensive microfilm collection aided in our research
of past significant weather events, and their wonderful
photograph collection added greatly to our text. We would
also like to acknowledge Phillip Earl, curator emeritus of
the Nevada Historical Society. He generously shared with
us the results of his research into the incredible winter of
1889–90. The staffs at both the Getchell Library and the
Washoe County Public Library were of assistance throughout our research in providing access to microfilm and other
records when needed.
Appreciation is also extended to Gail Prockish, Environmental Engineer II at the Washoe County Department
of Water Resources, for creating maps which compared the
areas in Reno that were affected by the January 1997 flood
and the New Year’s Eve 2005 flood. The authors would
also like to thank Randall Osterhuber of the Central Sierra
Snow Laboratory (CSSL) for creating the original graph
depicting the snowfall and snow depths recorded at that
location from the late 1870s to the early 21st century.
Many people helped in the review process of this
manuscript. The authors would like to thank Roger Lamoni
(former Warning Coordination Meteorologist at the NWS
office in Reno, and now at NWS Western Region Headquarters), Jim Fischer (Science and Operations Officer),
and Jane Hollingsworth (Meteorologist-in-Charge) (both at
As with any project, this one could not have been completed without the assistance of a whole host of people.
Before the writing could begin, data had to be collected
and analyzed. Data for this climatology were derived from
a variety of sources. Average values for various parameters
were taken from the 1971–2000 climatological normals for
Reno, Carson City, and Tahoe City. Actual observed data
for these weather parameters are from the monthly Local
Climatological Data (LCD) sheets for Reno. Data for
Carson City, Nevada and Tahoe City, California were
procured from the Western Regional Climate Center
(WRCC) website, and from the National Climatic Data
Center (NCDC). Weather observations from Carson City
and Tahoe City are supplied by NWS cooperative observers. Official data for Reno is from U.S. Weather Bureau
and National Weather Service observations. Climate information was also accessed using the XMClimate software
program (Petrescu, 1998).
Missing data were supplied by the Western Regional
Climate Center in Reno and the Nevada State Library and
Archives in Carson City. Kelly Redmond, Jim Ashby, and
the rest of the staff at WRCC were extremely generous in
answering questions. We would also like to thank WRCC
for the use of their computer program to generate the wind
roses in this publication. Finally, we would like to thank
Kelly and Jim for assisting us at the National Weather
Service in estimating the snowfall that was experienced at
the Reno Airport during the incredible snowstorms of late
December 2004 and early January 2005. At that time, the
official snowfall and snow depth data for Reno were collected by cooperative weather observers at the Nevada
Humane Society, located just east of the Reno airport.
These observers were not able to make it in to Reno because of the impassable roads. Without the collaboration
mentioned above (using extensive snowfall, precipitation,
and snow density data reported from other sites around the
region) an accurate estimate of these historic snowstorms
would have been unavailable.
The staff members at the Nevada State Archives were
invaluable in providing access to data that we did not have.
Archivist Christopher Driggs and manager Jeffrey Kintop
were especially helpful in providing access to actual
weather observation forms from the late nineteenth and
early twentieth centuries for both Carson City and Reno.
This information included weather observation reports
from Carson City during the 1890s, and U.S. Weather
Bureau weather observation forms for Reno for the period
1906 through 1937. These forms allowed us to supplement
data that we were missing from these periods.
72
and climate phenomena abundantly clear. Jennifer Mauldin
of the Nevada Bureau of Mines and Geology (NBMG)
contributed photographs showing snow cover across western Nevada. Chris Ross, Mark Vollmer, and Jack Hursh
also contributed many excellent photographs of various
weather phenomena. The Nevada Historical Society made
available numerous photographs showing weather conditions from the past across the region. Kris Ann Pizarro,
supervising cartographer at NBMG, went out of her way to
take photos of weather conditions even as this book was
being written. Her dedication to gathering appropriate
photographs for this publication is deeply appreciated.
Finally, the authors would like to thank Dick Meeuwig,
Kris Ann Pizarro, Gary Johnson, and the rest of the staff at
the Nevada Bureau of Mines and Geology for their guidance throughout the publication process. Dick was always
helpful and was able to make clear what needed to be done
in order to complete the publication process successfully.
Kris was always generous with her time and was ever
willing to answer any questions as they arose. She truly
took on this project as her own, and her enthusiasm kept
the authors going during those times when progress to
them seemed slow. She created many of the figures used in
this publication. And Gary’s graphical expertise gave us
maps that were truly worth a thousand words. Liz Crouse,
Jack Hursh, and Jennifer Mauldin were also involved in
seeing this book to publication. All of them were consistently a pleasure to work with, and the authors would
gladly go through the experience again.
Photo by Jack Hursh
the National Weather Service Forecast Office in Reno) for
reviewing the draft of this manuscript for accuracy and
thoroughness. Their comments were extremely beneficial
in improving the final document. Both Jane and Jim gave
continual support and encouragement to the authors
throughout the research and writing of this book. We
would also like to thank Rhett Milne, Warning Coordination Meteorologist (and former Fire Weather program
leader) at the NWS office in Reno for his helpful review of
the wildfire section.
Sincere appreciation is extended to Hal Klieforth
(Research Meteorologist Emeritus at the Desert Research
Institute (DRI) in Reno, and associate state climatologist
for Nevada), Jeffrey Underwood (Nevada State Climatologist, and assistant professor in the Department of Geography at the University of Nevada, Reno), Jim Ashby
(climatologist at the Western Regional Climate Center in
Reno), and Rachel Dolbier (Administrator of the W.M.
Keck Earth Science and Mineral Engineering Museum at
the University of Nevada, Reno) for thoroughly reviewing
the manuscript as part of the publication process. Their
insightful suggestions were invaluable in making this a
better document.
Photographs have added greatly to this book and the
authors would like to thank those persons who offered
photos for publication. John James contributed photographs from his collection. His photos of deep snowfall, of
drought conditions, and of flooding in the Lake Tahoe
basin and in Reno help to make the effects of these weather
Snow on Peavine Mountain.
73
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76
Glossary
Diurnal – Referring to the normal variation in atmospheric
elements throughout a period of 24 hours. The typical
diurnal variation in temperature is for the air mass to
cool at night, reaching its lowest point around sunrise.
The temperature then rises throughout the day, reaching
its highest reading usually in late afternoon or early
evening. The relative humidity shows an opposite
pattern, reaching its highest reading around sunrise, and
then reaching its lowest levels in late afternoon.
Acre-foot – The volume of a substance (e.g., water) that
would cover an area of 1 acre to a depth of 1 foot.
Advection – The horizontal movement of an atmospheric
element such as heat, moisture, or fog.
Airflow – The movement of air at the surface or at various
levels in the atmosphere.
Air mass – A body of air that contains nearly uniform
constituents such as heat or moisture.
Downburst – The downward rush of air produced in a
thunderstorm or high-based cumulus cloud. This
downward-moving air reaches the ground and then
spreads out in all directions. If it hits the ground at an
angle, most of the strong wind will move in that
direction. Wind speeds can approach 100 mph and
cause extensive damage. Damage caused by a downburst can be distinguished from that caused by a
tornado because the damage from a downburst tends
to lie in the same direction on the ground. By contrast,
the damage from a tornado will reflect the rotating
motion of the tornado.
Antecedent conditions – The conditions of the soil before
a weather event. If the soil is saturated, then there is a
greater chance that there could be flooding due to
runoff from heavy rainfall.
Anticyclone – An area of relatively high pressure. The air
in this region tends to subside (move downward in the
atmosphere). When the air reaches the surface it
spreads outward and blows in a clockwise direction
around the center of high pressure.
Atmospheric pressure – The weight of a column of air
from the ground up to the edge of space. The weight of
this column is measured by a barometer in a variety of
scales: millibars, inches of mercury, among others.
Drought – A long period of below normal precipitation
sufficiently long enough to cause a serious hydrological imbalance.
Cold front – The area of transition between cold air moving into a region and the warmer air it is replacing.
Dust devil – A rotating column of air which forms as a
result of a hot surface generating strong convection.
This relatively warm air then rises and begins to rotate.
Wind speeds are considerably less than those in a
tornado, but can still cause damage.
Condensation – The process which occurs when a substance (such as water) changes from the gaseous to the
liquid state.
Evaporation – The process which occurs when a substance (such as water) changes from the liquid to the
gaseous state.
Convection – The vertical movement of heat in an air
mass. Convection is responsible for the formation of
clouds. Strong convection can lead to the formation of
cumulonimbus clouds and thunderstorms.
Evapotranspiration – The combination of evaporation
and transpiration. Plants release water vapor to the
atmosphere. Evapotranspiration refers to the addition
of moisture to the atmosphere from things such as
bodies of water or snow cover (evaporation) and from
plants (transpiration).
Cumulonimbus – A type of cloud that forms during unstable conditions. This is the typical “thunderstorm
cloud.” It is sometimes referred to by the initials
“CB.” The tops of cumulonimbus clouds range from
as low as 25,000 ft in the cooler half of the year, to as
high as 40,000 ft during the summer in this region of
Nevada and California. CBs can produce tornadoes,
large hail, strong damaging winds, and lightning.
Filling – The process of a low pressure system increasing
in pressure and thereby becoming less intense.
Fog – Suspended visible water droplets in the atmosphere.
Cyclone – An area of relatively low pressure. The air in
this region tends to rise. Air outside of this region of
low pressure circulates in a counterclockwise direction. Air is pulled into the cyclone to fill the area left
by the rising air at the center.
Freezing fog – Fog that forms when the temperature is
below freezing. Sometimes called pogonip.
Freezing level – The altitude in an air mass at which the
temperature of the air is 32º F (0º Celsius). It is
important for forecasters to know the freezing level in
an air mass because this will indicate where snowflakes in the colder air above the freezing level will
start to melt and turn into raindrops as they fall
through the warmer air below the freezing level. This
can also help to indicate at what elevations snowfall
will accumulate.
Deepening – The process of a low pressure system dropping in pressure and thereby becoming more intense.
Depression – Another name for a region of low pressure.
Dew point – The temperature at which a parcel of air becomes saturated if it is cooled at a constant pressure.
77
close to the ground. Since warm air is above colder air,
an inversion is a relatively stable layer. An air parcel
that undergoes lifting will rise into the region of
warmer air. Since the air parcel is colder (and thus
more dense) than the warmer air surrounding it, it will
sink back to the surface. This is why inversions are
such notorious fog producers. The cold air sits near the
surface and does not mix with warmer air above it.
Freezing rain – Type of precipitation that results from
raindrops falling through a layer of an air mass that is
warmer than 32º F, then falling through a layer near
the ground that is colder than freezing. The raindrops
do not have time to turn into ice pellets (sleet) but
freeze instantly when they hit any surface that is colder
than freezing.
Front – The area of transition between a cold air mass and
an adjacent warm air mass.
Jet stream – A region of strong winds in the upper
atmosphere. Jet streams are formed from differences in
temperature which create pressure gradients. The
pressure gradient (difference in pressure across an
area) accelerates the air that is moving through this
area. There are two main jet streams over the Earth’s
northern hemisphere (north of the equator). The polar
jet circles the globe at around 50 to 60° north latitude.
The generally weaker subtropical jet is located at
around 20 to 30° north latitude.
Frost – Ice crystals that are formed on surfaces that are
colder than freezing.
Glaze – A coating of ice caused by freezing rain.
Hail – Precipitation that is formed in cumulonimbus
clouds. A hailstone starts as an ice particle. As it falls
through the cloud it accumulates a covering of water.
As it is then forced upward through the cloud the
covering of water freezes. A hailstone makes many
passes through the cloud until it becomes too heavy for
the thunderstorm updraft to keep it aloft. These
multiple passes through the cloud are what causes the
layering of a hailstone. Very large hailstones are rare
in the Great Basin because, among other things, they
partially melt as they fall through the very dry air
below the cloud base.
Lake effect snow – Snowfall that is generated from cold
air passing over relatively warmer water. The instability that results allows for convective clouds to develop
and increases the possibility of snow to fall.
Lenticular cloud – A high-level cloud that is formed by
the upward motion in thewave that forms in an air
mass in the lee (downwind) of mountains and/or
mountain ranges. These clouds have a lens (lenticular)
shape because of the air’s motion through the wave.
As the air rises and cools in the wave, water vapor is
condensed into clouds. Then, as the air in the wave
begins moving downward and warms, the cloud
droplets evaporate. This undulating motion causes a
wave cloud to have a lens (lenticular) shape with its
characteristic rounded top and fairly flat base.
Headwater – The upper reaches of a river, creek, or
stream.
High – (see Anticyclone).
Humidity – A measure of the amount of moisture in an air
mass.
Hydrology – The science of water and its interaction with
the earth’s surface and subsurface.
Lightning – An electrical discharge which results from the
difference in electrical charges between the Earth’s
surface and a cloud. The rapid expansion of the
resulting column of heated air is the sound that we
refer to as thunder.
Ice pellets (sleet) – Precipitation that results when
raindrops fall into a layer of cold air near the surface
and freeze before hitting the ground. If the cold air at
the surface is not deep enough to cause the raindrops
to completely freeze, then they freeze on contact with
surfaces when they reach the ground (this is the
definition of freezing rain).
Low – (see Cyclone).
Macroburst – A downburst with winds extending beyond
2.5 miles (4.0 kilometers) from its center.
Insolation – (from INcoming SOLar radiATION) The
amount of radiation from the Sun that reaches the
Earth’s surface (that which is not reflected or absorbed
by clouds or the atmosphere).
Mainstem - The main part of a river, as opposed to the
tributaries which feed into it.
Microburst – A downburst with winds extending 2.5
miles (4.0 kilometers) or less from its center. In the
Great Basin microbursts tend to by “dry,” meaning
that little or no rainfall associated with them reaches
the ground.
Instability – The vertical state of the atmosphere in which
the temperature decreases with altitude, i.e., the lapse
rate is greater than the rate of cooling of a parcel of air
subject to the process of lifting, thus making the parcel
more buoyant than the ambient air and allowing the
parcel to rise until it encounters an inversion or a layer
with a more stable lapse rate.
Millibar – A unit of pressure. The abbreviation for
millibar is mb.
Inversion – The situation in which relatively cold air
underlies warmer air aloft. Inversions are often caused
by an extensive snow cover cooling the layer of air
Pogonip – A word of Native American origin (meaning
“white death”) which is referred to, by some, as
freezing fog, which forms in very cold air. The word
78
pogonip has also come to be used by local people
living in western Nevada to refer to the rime which
coats surfaces as a result of freezing fog.
would be in it if the air mass was saturated. If an air
mass is saturated it means that evaporation from that
air mass equals the condensation occurring in the air
mass; its relative humidity is 100%. If an air mass is
not saturated (the usual case) then evaporation is
exceeding condensation and its relative humidity will
be some percentage less than 100%.
Polar air – An air mass that has resided over cold polar
regions (such as central Canada or central Siberia).
The snow covered ground causes the air mass to
become extremely cold. This cold air is then transported to lower latitudes as the air mass moves out of
its region of origin.
Return period – The average period of time between
events of a given magnitude. For example, there would
be a 1 percent chance that a one-hundred-year flood
would occur at a given location in any given year.
Polar jet – (see Jet Stream).
Precipitation – Water or ice particles that form in clouds
and then fall to the surface. Since temperatures in
clouds are often below freezing, it is usually snow that
forms from the aggregation of ice crystals. If the air
below the cloud base is colder than freezing, then the
snowflakes will reach the ground without melting. In
warmer weather the snowflakes melt into raindrops
and reach the surface as rain. If there is a below
freezing layer near the surface, depending on the depth
of the cold air, raindrops falling through this cold layer
will reach the ground as either freezing rain or ice
pellets (sleet). Hail is also considered precipitation
since it forms in clouds and then falls to the ground.
Ridge – A (usually elongated) area of high pressure.
Rime – The coating of ice that forms on surfaces when the
temperature of an air mass is below freezing.
Ripe (snowpack) – The condition of snow that is ready to
melt. The density of the snowpack (when the snow is
near freezing) is generally greater than 4 parts water to
10 parts snow (so, for example, if 10 inches of ripe
snow was melted, it would result in around 4 inches of
liquid water equivalent).
Runoff – Water (from rainfall or snowmelt) that cannot be
absorbed by the ground. This can cause flash flooding
or contribute to river flooding.
Pressure – See Atmospheric pressure.
Saturation – The characteristic of an air mass in which
evaporation in the air mass equals condensation. Any
additional condensation would result in the formation
of clouds, precipitation, or fog. Also, the characteristic
of the soil in which the soil cannot absorb any more
water. Any water coming into contact with the soil
would not be absorbed but would run off.
Pressure gradient – The change in pressure between an
area of high pressure and an area of lower pressure.
Air flows from the area of high pressure to the area of
low pressure (this movement of air is what we define
as wind). A relatively stronger pressure gradient would
thus produce a stronger wind.
Radiation – Energy from the Sun which passes through
space at the speed of light. As radiation passes through
the Earth’s atmosphere some parts of the radiation’s
spectrum are reflected by clouds and by ice and snow
at the Earth’s surface, and some is absorbed by clouds,
water vapor, carbon dioxide, suspended particles, and
other matter in the atmosphere. That which is received
by the Earth’s surface is absorbed as heat energy
which, in turn, warms the lower atmosphere by the
processes of conduction and convection. At night,
with a clear sky, the ground re-radiates some of its
infrared (heat) energy back to space, leaving the lower
near-surface air at its minimum temperature near
dawn. This diurnal cycle accounts for the large daily
temperature ranges experienced during much of the
year in our region.
Sleet – (see Ice pellets).
SNOTEL – (for SNOwfall TELemetry) An observing
system that transmits snow water equivalent, snow
depth, precipitation, and temperature data in near real
-time usually from mountainous sites .
Snow level – Similar to freezing level. The snow level is
the elevation above which precipitation is generally
in the form of snow.
Stability – A measure of how easily an air parcel would
continue rising if it were forced upward. (for more
discussion see Instability).
Stable layer – A layer of the atmosphere in which warmer
air overlies cooler air. In this situation, if an air parcel
is forced to rise through the air mass, it will cool as it
rises, thus being cooler than the warmer air it is rising
through. Since it is cooler than the surrounding air, its
ascent will slow and the air parcel will then fall back
to the level it started from. Inversions are examples of
stable layers.
Rain shadow – The area to the lee of a mountain range
which receives a significantly lower amount of
precipitation than the windward side of the range.
Reach (river) – The length of a river channel, generally
between two major tributaries, which is fairly uniform
in its discharge and its slope.
Stage-discharge relationship – The relationship between
the stage at a river gage and the corresponding flow of
the river at that point.
Relative humidity – The ratio of how much water vapor is
in an air mass compared to how much water vapor
79
Stationary front – The area of transition between an area
of warm air and an area of cold air. A front is defined
as stationary (or quasi-stationary) if it is not moving
much, if at all.
Warm front – The area of transition between cold air that
is moving out of a region and the warmer air that is
replacing it.
Washoe Zephyr – The westerly (from the west) winds that
frequently occur in the lee of the Carson Range,
especially during the warmer half of the year. The
name is derived from the term for a west wind
(zephyr).
Storm track – The path that cyclones (low pressure
systems) follow. Over the western United States
typical storm tracks are through the Pacific Northwest
during the summer. During the winter the storm tracks
move south and low pressure systems often move
through California and the Great Basin.
Water equivalent – The amount of water contained in an
amount of snow when the snow has been melted. This
amount is recorded as the precipitation amount
(precipitation is from either rainfall or melted snow).
Sublimation – The process which occurs when a substance
(such as water) changes directly from the frozen to the
gaseous state without passing through the liquid phase.
The opposite process is referred to as deposition
(however, it is sometimes also referred to as sublimation) in which a substance (such as water) changes
directly from the gaseous state to the frozen state
without passing through the liquid state.
Waterspout – A rotating column of air that is almost
always appended to a cloud base and forms over a
body of water. Waterspouts form from cumulus
clouds, thus they form under different conditions than
tornadoes. Waterspouts are much weaker than
tornadoes, but still can cause some damage, so boaters
are advised to steer clear of them.
Subsidence – The situation in which air descends to lower
levels. Subsidence occurs in the center of high pressure areas. As the subsiding air reaches the ground
surface it moves out in all directions. This subsiding
air warms as it moves to lower levels, thus reducing
the chance of cloud formation. This is the reason that
areas of high pressure usually have clear skies.
Water vapor – Water in the gaseous state. Water vapor is
always present in the atmosphere but is not visible.
Water year – The period (12 months) in which precipitation is recorded for hydrological purposes. A water
year runs from October 1 through September 30 of the
following year. A water year is designated by the year
during which it ends (for example, the water year 1977
would run from October 1, 1976 through September
30, 1977).
Subtropical jet – (see Jet Stream).
Supercell – An intense long-lasting cumulonimbus cloud.
Due to its tilt, a supercell’s updraft and downdraft do
not interact, thus allowing the cloud to last for a
relatively long period of time, perhaps up to an hour or
more. Because of this long life-cycle, large hail and
strong damaging downdraft winds can result. However, due to the dry conditions over the region,
supercells are rare over the western Great Basin.
Wave cloud – The type of cloud that is formed as a result
of the motion of the air downwind of an obstacle such
as a mountain or mountain range. As the air travels
downwind from a mountain range it moves in an
undulating manner as a result of its motion being
disrupted. As the air moves downward it warms and
dries so, as a result, clouds do not form. As the air
starts to ascend it cools and a cloud forms. Farther
downwind the process continues and as the air descends the edge of the cloud evaporates. This process
can continue for tens of miles downwind of the
obstacle. Wave clouds are sometimes called lenticular
clouds because of their lens shape.
Synoptic-scale – In meteorology this refers to large-scale.
An example of a synoptic-scale system would be a
large area of low pressure or high pressure which
covers much of the United States.
Synoptic pattern – This is a weather pattern that covers a
large area such as much of the United States. Largescale weather systems of this size are referred to as
synoptic-scale systems.
Wind rose – A diagram depicting the percentage of time
(for a day, month, year, etc.) that the wind blows out
of various directions (typically eight or sixteen
compass points). For each of the compass points, the
length of the bar indicates the percentage of time that
the wind blows from that direction.
Telemetry – The process of transmitting meteorological or
hydrological data via electronic means (e.g. telephone
line, radio waves, or by satellite).
Tornado – A violently-rotating column of air appended to
a cumulonimbus (thunderstorm) cloud.
Trough – A (usually elongated) area of low pressure with
higher pressure on either side of its axis. On pressure
charts a trough is usually depicted in the shape of a U
or V, or an inverted (upside-down) U or V.
80
Appendix A. Weather Station History
Reno
When analyzing the climate of a region, changes that have
taken place in the observation of weather conditions in the
area should be considered. The official weather observation
site in Reno has changed a number of times during the last
130 years. Starting in December 1870, daily rainfall
observations were taken by the Southern Pacific Company
agent at the Southern Pacific Depot at Commercial and
Lake Streets in Reno. On January 1, 1888, the official
weather observation site was changed to the Administration Building (Morrill Hall) on the University of Nevada
campus north of downtown Reno.
Beginning in November 1905 the U.S. Weather
Bureau took weather observations from the ThomaBigelow Building at First and Virginia Streets in downtown Reno. In March 1910 the observing site was changed
to the I.O.O.F (Odd Fellows) Building at Second and North
Center Streets in Reno. In March 1934 weather observations were taken at the Post Office Building at South
Virginia and Mill Streets. Official weather observations
were taken at the Post Office Building until the end of
August 1942.
With the opening of an airport southeast of town,
pilots needed weather observations and forecasts. In
January 1931 the U.S. Weather Bureau started taking
observations at the airport (Hubbard Field). This was a
significant change in that weather observations were now
being taken in what could be considered to be almost a
rural location. On September 1, 1942, the airport became
the official observation site for Reno (and has remained the
official site to this day). The effects of this change in
location are more pronounced in the temperature record
than in the precipitation data (Table A).
From the beginning of the century through the 1930s,
the average annual temperature at Reno increased 0.5 to
1.0ºF per decade. This may be partially the result of the
growth of the downtown area and the simultaneous
transition during the early twentieth century from wooden
buildings to more brick and stone structures that retain
more heat. After the official Weather Bureau observation
site was moved to the airport southeast of town the average
annual temperature reported during the rest of the 1940s
was almost 3.0ºF cooler than it had been during the 1930s
and first few years of the 1940s when the observation site
was still downtown. The average annual temperature then
increased less than 0.5ºF per decade through the 1970s. In
fact, there was practically no change in average annual
temperature through the 1960s and 1970s. During the
1980s and 1990s the average annual temperature increased
at a faster rate (between around 1.0 and 2.0ºF per decade).
This is probably due to the “heat island” effect caused by
the airport runways and pavement and the increased
habitation and use of the area surrounding the airport.
No such pattern can be discerned in the precipitation
data. The annual precipitation totals are more sensitive to
individual events than are the average annual temperatures.
The average temperature for the day is only one of 365
such values that will be averaged together for that year. By
contrast, a few very large snowstorms during a particular
decade can skew the data. In just one day one large winter
snowstorm or spring rain shower can deposit a tenth of
Reno’s annual precipitation. An example of the significance of this precipitation data can be seen during the
drought years from the mid 1920s through the early 1930s.
During the first few years of the decade an inch or more of
precipitation was reported at Reno on one or two days each
year. However, after 1.02 inches of precipitation (0.20
inches of this from melted snow) was reported on December 13, 1922, it was seven years before at least an inch of
daily precipitation was again recorded at Reno when 1.13
inches of rain fell on December 10, 1929.
After the move to the airport in September 1942, the
next change in observation site at Reno occurred in June
1949 when the weather observation equipment was moved
60 feet to the south to the CAA Building at the airport.
Another change took place in October 1959 when the
equipment was moved 0.8 mile to the north-northwest to
the Federal Facilities Building at the airport. In August
1980 the observing equipment was moved a quarter-mile to
the east-southeast to the General Aviation Building on the
airport grounds.
Table A. Average annual temperature (ºF) and precipitation (inches) per decade during the twentieth century
at Reno.
Decade
Temperature
Precipitation
1900–1909
49.8
8.60
1910–1919
50.2
8.15
1920–1929
51.0
6.92
1930–1939
51.9
6.99
1940–1942
51.7
8.19
Official weather observations relocated from downtown Reno to Reno airport (Hubbard Field) starting
September 1, 1942.
81
1943–1949
49.0
6.04
1950–1959
49.2
7.76
1960–1969
49.5
7.70
1970–1979
49.5
7.05
1980–1989
51.2
7.86
1990–1999
52.3
7.65
On May 1, 1923, the Sierra Pacific Power Company
office on Main Street in Carson City became a cooperative
observer for the U.S. Weather Bureau. In June 1941 the
observation site was transferred to the roof of the Laboratory Building of the Nevada Department of Highways at
the northwest corner of West Second and Carson Streets. In
July 1951 the observation location was moved two blocks
east to the State Office Building on Fall Street between
Second and Third Streets.
In May 1965 the observing site was moved 0.4 miles
south to the new Highway Testing Laboratory and Headquarters Building of the Nevada Department of Highways.
In May 1984 Station House #3 of the Carson City Fire
Department (on North Curry Street) became the official
cooperative weather observer for Carson City. This was 2
miles south of the previous location. In June 1992 the
location of Station House #3 was changed to 777 South
Stewart Street.
Weather observations were taken at the Reno airport
(through all of its subsequent name changes) by Weather
Bureau (and later National Weather Service (NWS))
personnel from 1931 until 1995. A significant change
occurred on September 1, 1995 when an automated
weather observing system was commissioned at the Reno
airport. On May 5, 1998, this automated observing system
was moved from the south end of the airport runway to its
current location at the north end.
This automated system is a new way to take weather
observations and this should be taken into account (as
would changes in location) if any change in weather
patterns or climate is noticed in the future (Arndt and
Redmond, 2004). A significant drawback with this automated system is that snowfall and snow depth observations are not taken. This effectively ended snowfall and
snow depth data for the Reno airport location until the fall
of 2004 when a cooperative weather observer near the
airport started recording snowfall and snow depth data.
Tahoe City
Cooperative weather observations have been taken at Tahoe
City since 1914. The observation site has been in virtually
the same location until present. The Tahoe station started out
at latitude 39º10'N and longitude 120º10'W in the Truckee
River valley at an elevation of 6500 feet, approximately 500
feet from Lake Tahoe. In August 1950 the equipment was
moved approximately 125 yards east of its former location
to the other side (south bank) of the Truckee River about
one-half mile southwest of the U.S. Post Office in Tahoe
City, and 300 feet south of the mouth of the river. The
station was at the same latitude but the new longitude was
120º08'W and the new elevation 6230 feet.
In July 1960 the name of the station was changed from
Tahoe to Tahoe City, to agree with that of the post office.
In September 1971 the equipment at the Tahoe City
location was moved 475 feet to the north-northeast, to a
location 425 feet south of the Lake Tahoe outlet.
Carson City
According to the Nevada State Library and Archives,
Charles W. Friend started taking weather observations in
Carson City in 1880. His weather observatory was a block
from the state capitol. In 1887 the Nevada state legislature
established a Nevada State Weather Service, and Friend
was appointed as its first director. After the establishment
of the U.S. Weather Bureau in 1890 weather observers
from the Bureau were assigned to assist Friend in Carson
City. Starting in 1892 a representative from the Weather
Bureau held the position of assistant director of the Nevada
State Weather Service. The state weather service continued
until 1905 when responsibility for official weather observations was transferred from personnel in Carson City to the
Weather Bureau office in Reno.
82
The Nevada Bureau of Mines and Geology (NBMG) is a research and public service unit of the University of
Nevada and is the state geological survey. NBMG is part of the Mackay School of Mines at the University of
Nevada, Reno. NBMG scientists conduct research and publish reports on mineral resources, engineering
geology, environmental geology, hydrogeology, and geologic mapping. Individuals interested in Nevada geology
are encouraged to visit, call, or write NBMG or visit our homepage at www.nbmg.unr.edu.
NBMG publications and maps, U.S. Geological Survey maps, and related publications can be purchased at the
Publication Sales Office or ordered over the Internet at www.nbmg.unr.edu/sales.htm.
Orders for publications or requests for information may also be made by telephone, fax, e-mail, or U.S. Mail.
Phone: (775) 784-6691
Phone hours: 7:00 a.m. to 4:00 p.m., Monday –Friday
Fax: (775) 784-1709
E-mail: (orders) [email protected]
(information) [email protected]
U.S. Mail: Nevada Bureau of Mines and Geology
Mail Stop 178
University of Nevada
Reno, NV 89557-0178
Fog and frost rime in a pine forest in the Carson Range,
March 2005.
Photos by Heather Angeloff
The University of Nevada, Reno is an Equal Opportunity/Affirmative Action employer and
does not discriminate on the basis of race, color, religion, sex, age, creed, national origin,
veteran status, physical or mental disability, and in accordance with university policy, sexual
orientation, in any program or activity it operates. The University of Nevada, Reno employs
only United States citizens and aliens lawfully authorized to work in the United States.
Manuscript reviewed by:
Jim Ashby, Western Regional Climate Center, Reno
Rachel Dolbier, W.M. Keck Museum, UNR
Hal Klieforth, Desert Research Institute, Reno
Jeff Underwood, Department of Geography, UNR
Editing and layout: Dick Meeuwig
Graphics and photo enhancement: Kris Ann Pizarro
and Jennifer Mauldin
Production: Jack Hursh
First edition, first printing, 2007, 1000 copies
Printed by: Bear Industries, Sparks, Nevada
Photo by Jack Hursh
Photo by Mark Vollmer
Downtown Reno, 2002. Snow is falling on Slide Mountain (elevation 9694 feet) in the background.
Note the avalanche paths down the middle part of the mountain with ski runs on both sides.
Southern Reno, looking northeast toward a rainstorm beyond the Huffaker Hills.