Climate in Southeast Idaho
Pocatello is located at the mouth of the Portneuf
Canyon along the southeastern edge of the Snake River
Plain. The elevation of the city is approximately
4500 feet above mean sea level. Generally mountainous
terrain borders the city on the east and south. The
mountains rise abruptly to over 9000 feet elevation
within 15 miles to the east, and to over 7500 feet
elevation 10 miles south. The broad Snake River valley
extends to the west and north with intensive agriculture
practiced in the immediate area. A desert composed
mostly of lava rock along with sagebrush and sand
is located approximately 25 to 30 miles north and
west of the city.
Pocatello's climate is characterized by variety.
The area's semi-arid climate is the result of the
Cascade and Sierra mountains to the west and the Bitterroot
and Rocky Mountains to the north which effectively
block Pacific moisture. Summer monsoonal moisture
intrusions are infrequent and significantly modified
by the arid Great Basin of Utah and Nevada. The Rocky
and Bitterroot Mountains form the headwaters of the
Snake River and receive copious amounts of winter
snow. The success of local agriculture is dependent
on irrigation, both from deep wells and a system of
canals supplied by storage reservoirs on the Snake
During winter, brisk southwesterly winds often persist
for days or weeks. These winds may moderate cold winter
conditions, producing unusually mild temperatures compared
to surrounding areas. There are usually a number of
days each winter when temperatures remain below freezing.
Sub-zero temperatures usually occur only a few days
each winter. During especially cold outbreaks, snowfall
may accumulate to a depth of a foot or more. Cloudy
and unsettled weather is common during the winter with
measurable precipitation occurring on about one-third
of the days.
Spring months are normally wet and windy. Winds of
20 to 30 mph may persist for days at a time. Weather
conditions fluctuate quickly during the spring. Afternoon
temperatures in the 30s and 40s with precipitation in
the form of rain or snow may occur after a period of
sunny skies and afternoon temperatures in the 60s or
70s. Thunderstorms are not uncommon, and are usually
accompanied by rain showers and occasional snow. Low
elevations snow pack usually melts quickly during the
spring, but high elevation snow pack can persist into
Summer may begin suddenly with a rapid change to warm
and dry weather. Home heating is usually not required
after the first week in June, but chilly nights can
persist into early July. Showers and/or thunderstorms
are common from late spring through summer. These storms
often produce very localized precipitation. Thunderstorms
are seldom severe, and tornadoes occur infrequently
in the area. Brief heavy rain, lightning, small hail,
and gusty winds may cause very localized damage at times.
Long periods of excessively hot weather in July and
August are uncommon. Afternoon temperatures often rise
into the 90s, however low humidity usually results in
overnight temperatures in the 50s or even cooler. The
average growing season in Pocatello is around 120 days,
extending from late May to late September.
Autumn ushers in cooler weather with daytime highs
generally in the 70s in early fall dipping into the
mid 40s by mid November with generally dry conditions.
Autumn storms are usually very fast moving, and seldom
persist for more than a few days. Sunny, warm days
with cool nights are delightful for outdoor activities.
Continuous home heating is seldom needed until mid
October. The first cold wave with highs below 20 and
lows around 0 or lower may arrive anytime between
late November and Christmas.