Boise, ID climate
Boise has chilly winters and hot summers, with very little rain. A typical July afternoon reaches 93°, a January night drops to 24°, and about 18 inches of snow falls in a normal winter.
NOAA 1991-2020 climate normals Updated once a decadeWhat a year in Boise feels like
Winter
Spring
Summer
Fall
Boise weather by month
Average highs, lows, rain and snow for every month, from NOAA’s 1991–2020 normals.
| Month | High | Low | Rain + melt | Snow | Wet days | Snow on ground | 30-yr range |
|---|---|---|---|---|---|---|---|
| January | 39° | 24° | 1.6" | 5.3" | 11 | 6 | 20° – 38° |
| February | 47° | 27° | 1.1" | 3.3" | 9 | 3 | 29° – 43° |
| March | 57° | 33° | 1.4" | 1.2" | 10 | 1 | 40° – 50° |
| April | 64° | 37° | 1.3" | 0.1" | 9 | 0 | 45° – 56° |
| May | 73° | 45° | 1.5" | 0 | 8 | 0 | 53° – 65° |
| June | 82° | 51° | 0.8" | 0 | 5 | 0 | 62° – 75° |
| July | 93° | 59° | 0.2" | 0 | 2 | 0 | 65° – 82° |
| August | 91° | 57° | 0.2" | 0 | 2 | 0 | 68° – 77° |
| September | 81° | 48° | 0.4" | 0 | 4 | 0 | 60° – 68° |
| October | 66° | 37° | 0.8" | 0.1" | 6 | 0 | 44° – 58° |
| November | 50° | 30° | 1.3" | 2.0" | 10 | 2 | 32° – 47° |
| December | 39° | 24° | 1.7" | 5.6" | 12 | 6 | 23° – 37° |
| Year | 65° | 39° | 12.2" | 17.6" | 89 | 17 |
“Wet days” have at least 0.01" of rain or melted snow. “Snow on ground” counts days with 1" or more. The 30-year range is the coldest and warmest that month’s average temperature got between 1991 and 2020.
Rain and snow in Boise
Boise gets 12 inches of rain and melted snow a year. December is the wettest month and August the driest. Rain or snow falls on about 89 days a year. Snow covers the ground about 17 days of the year.
About 179 frost-free days a year
In half of years the last 32° night comes by April 24 and the first one by October 21. That leaves about 179 frost-free days for gardens, longer than 51% of U.S. towns.
Heating and cooling a home in Boise
Engineers use “degree days” to estimate how hard a furnace or air conditioner works. In Boise, 84% of that work is heating and 16% is cooling, so the furnace matters far more than the air conditioner.
Degree days measure how far each day’s average temperature falls below or rises above 65°, added up over a year. Source: NOAA station normals.
Boise and its neighbors
Boise borders 3 towns with climate data. January nights across them vary by 0.5°. Garden City has both the coldest January nights (24°) and the hottest July afternoons (93°). Boise’s January low is 24° and its July high 93°.
Temperatures and rain come from NOAA’s 5 km grid, so each town gets its own value.
How Boise compares
Compared with every U.S. town and city on TownTapestry, each counted once.
Warmer than it used to be
The last 30 years in Boise averaged 0.9° warmer than the 1900s. The biggest change is in January (+2.1°). The shift is smaller than in 77% of U.S. towns.
Change by month1991–2020 average minus 1901–2000 average, at Boise’s spot on NOAA’s grid
How much a month can swing
A normal is an average, and real years wander around it. January swings the most: between 1991 and 2020 its average temperature ranged from 20° to 38°. September is the most reliable, staying within 9°.
Common questions about Boise’s climate
What is the coldest month in Boise?
January, with a typical high of 39° and a low of 24°.
What is the hottest month in Boise?
July, with a typical high of 93° and a low of 59°. About 55 days a year reach 90°.
How much snow does Boise get?
About 18 inches in a normal winter, most of it in December.
When is the first frost in Boise?
In half of years the first 32° night comes by October 21, and the last spring frost by April 24.
What is the rainiest month in Boise?
December, with 1.7 inches of rain and melted snow. The year totals 12 inches.
Temperatures and rainfall come from NOAA’s gridded climate normals for Boise itself (about a 3-mile square). Snow, frost dates and day counts come from NOAA’s weather station at Boise Air Terminal, ID (2 mi) away. Normals are 30-year averages, not a forecast. Source: NOAA NCEI U.S. Climate Normals, 1991–2020 and 1901–2000.