Custer County Climate
Custer County, Idaho
Avg Annual Temp
40.8°F
Annual Precip
12.8"
Annual Snowfall
29.5"
Extreme Heat Days
11.966666666666669
days >= 90°F/yr
Monthly Temperature
Precipitation Calendar
Seasonal Overview
National Comparison
Climate Profile
About Custer County Weather
One of the Nation's Coldest Corridors
Custer County is significantly colder than the national median, posting a chilly annual average of 40.8°F. This mountain climate experiences some of the lowest average temperatures in the lower 48 states.
Well Below the Idaho Temperature Average
Averaging 40.8°F, Custer County is nearly 6 degrees colder than the Idaho state average of 46.5°F. It ranks among the state's coldest regions, characterized by long winters and short growing seasons.
Chillier Than Its Southern Neighbors
Custer County is much colder than nearby Elmore County, which averages 52.6°F. It also receives just 12.8 inches of precipitation, making it as dry as the high deserts to its south.
Frigid Winters and Brief Summer Heat
January temperatures average a freezing 18.5°F, while winter as a whole averages just 20.0°F. Summer provides a quick reprieve with a July average of 64.0°F and only 12 days topping 90°F.
Winterize for Extreme Mountain Cold
Extreme cold dominates the plan here, requiring high-efficiency heating systems and cold-weather survival kits for travel. Despite the cold, the 29.5 inches of snow is manageable compared to the state's wetter northern counties.
Frequently Asked Questions
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Data source: NOAA National Centers for Environmental Information (NCEI), U.S. Climate Normals 1991-2020.
Climate normals are 30-year averages of weather variables computed from 1991 to 2020. Station data is aggregated to county level using spatial averaging. Data is informational only — not a substitute for official National Weather Service forecasts or emergency weather warnings.