Rain
California's rain falls in intense thunderstorms, all-day soakers,
brief "sun showers," and slow but steady drizzle. The state's
average precipitation of 21 inches per year belies the extreme
variation from place to place. Yearly rainfall ranges from less
than 2 inches in Death Valley to 109 inches in the mountains along
the Oregon border. Across most of California, most of the precipitation
falls during the "rainy season" from October to April.
Snow
Snowfall amounts in California vary with elevation and latitude.
While every location in the state has seen snow at one time or
another, measurable snow is quite infrequent along the entire
coast; San Diego has reported flurries only twice in the 20th
century. Snow falls nearly every winter at elevations above 2,000
feet, and average snowfall is as great as 450 inches per year
in the high Sierras; many locations above 5,000 feet receive more
than 100 inches per year.
Record-setting California Weather
Hottest Ever: 134° F at Death Valley, July 10, 1913.
Coldest Ever: -45° F at Boca (north of Lake Tahoe), January 20, 1937.
Wettest Place: Monumental (a town in the Siskiyou Mountains): 109 inches average
precipitation (rain and melted snow) per year.
Driest Place: Death Valley: 1.78 inches precipitation per year.
Longest Rainless Spell: 993 days at Bagdad (east of Barstow), 1909-1912.
Snowiest Place: Tamarack (near Lake Tahoe): averages 450 inches per year, equivalent
to about 45 inches of precipitation.
Greatest Snowstorm: 189 inches at Mount Shasta Ski Bowl, February 13-19, 1959.
Lightning
Lightning is an electrical discharge between one part of a cloud
and another, between two clouds, or between a cloud and the earth.
In a typical year, lightning strikes California about 250,000
times (a relatively light occurrence of lightning), with perhaps
10 times as many flashes arcing across the skies without striking
the ground. About 20 percent of California's forest and brush
fires are ignited by lightning.
Thunderstorms
The sound of thunder is caused by explosive expansion of air heated
by lightning along a narrow (1- to 4-inch-wide) channel within
or extending from a cumulonimbus cloud. Thunder is therefore often
associated with heavy rain. Thunderstorms (as distinct from lightning
alone) are not very common in California, with annual frequencies
ranging from five or less in any given location along the coast
to about 20 in the Sierra Nevada.
Tornadoes
On average, only five tornadoes touch down in California each
year, making the state one of the least tornado-prone in the United
States. Most of these tornadoes are small, brief, and weak. The
bulk of California's tornadoes have occurred in the Los Angeles
Basin (as many as seven in a single day) and in the Central Valley.
Rainbow
Rainbows are taken as a cue that a storm is over. This is especially
true when storms move from west to east, and especially where
rain showers most often occur in the afternoon. These conditions
allow the setting sun to shine directly on the falling rain drops.
As sunlight enters the spherical drops, reflects off their interiors,
and exits back in the general direction of the sun, it is broken
into its component colors--the colors of the rainbow, ranging
from blue on the inside to red on the outside. If the sunlight
reflects twice off the inside of the drop, it comes out at a different
angle, causing a less common secondary rainbow, in which, because
of the second reflection, the order of the colors is reversed,
with red on the inside, and blue on the outside.
PHOTO: Joanne Huemoeller
