Photo: Jyoni Shuler · CC BY-SA 4.0Boise City is among the driest of U.S. towns: 12 inches of precipitation a year
In January the night’s low is typically 24°. Its July heat outdoes that of 91% of U.S. towns. Warming shows here too: 0.9° more than in 1901–2000, led by January. Picnics, hikes and garden evenings suit May, June and September, with highs of 73–82°.
A year in Boise City at a glance
Each month’s typical high and low, and what it brings.
What stands out about Boise City’s climate
Compared with towns across the U.S., with Boise City’s place in Idaho beside it.
What a year in Boise City feels like
Typical highs and lows by season and by month, from NOAA’s 30-year normals.
About 179 frost-free days a year
In half of years the last 32° night comes by April 24 and the first by October 21. Frost and day counts come from Boise Air Terminal, ID, Boise City’s official weather station (the one in National Weather Service reports), 2.2 miles from the city’s center point, at about the same height.
The 2023 USDA map puts Boise City’s center in zone 7a: the coldest night of a typical winter, averaged over 1991–2020, reaches about 5°. Plant labels use the zone; frost dates tell you when to plant.
Freezing nights by month
Average nights at or below 32°
90° days by month
Average days at 90° or more
About 18 inches of snow a winter
Snow, measured at Boise Air Terminal, ID, falls mostly in January and December. Precipitation (rain plus melted snow) adds up to 12 inches a year; December is the wettest month and August the driest. Rain or snow falls on about 89 days a year.
Rain + melted snow by month
Inches of water
Snowfall by month
Inches of snow
Heating and cooling a home in Boise City
84% of the work is heating. Months averaging under 55° run from October through April.
Degree days add up how far each day’s average falls below (heating) or rises above (cooling) 65° over a year. NOAA normals at Boise Air Terminal, ID.
Living with Boise City’s climate
What the numbers mean for a garden, a free afternoon and a bad-weather day.
179 frost-free days in zone 7a. The last frost comes by Apr 24 in half of years, so many gardeners wait a week or two past that to set out tomatoes. The first fall frost comes by Oct 21.
Months with highs of 62–84° and lows of 40° or more: May, June and September. 188 miles of trails are waiting.
Parks & trails →Of the yearly building losses FEMA expects in Boise City from natural hazards, river flooding is the largest share (62%); heat waves, cold waves, winter storms and ice storms together are 12%. Normals are averages; the hazards page covers the extremes.
Natural hazards →Boise City and its neighbors
Every town next door is within a degree of Boise City in January and July, closer than the 5 km grid can tell apart. Tap a town to see its climate.
Climates most like Boise City’s, farther away
TownRatings’ own comparison of NOAA 1991–2020 normals, not a NOAA product: places of 5,000+ at least 150 miles away, one per state, closest on January low, July high, precipitation and snow.
| Town | Jan. low | July high | Precip. | Snow |
|---|---|---|---|---|
| Boise City, ID | 24° | 93° | 12" | 18" |
| Magna, UT | 23° | 93° | 14" | 23" |
| Albuquerque, NM | 22° | 94° | 9" | 12" |
| Dalhart, TX | 21° | 92° | 16" | 20" |
| Chino Valley, AZ | 27° | 92° | 11" | 10" |
Temperatures and rain come from NOAA’s 5 km grid, so each town gets its own value. Snow and frost-free days come from the nearest weather station, so neighbors often share them.
Warmer than it used to be
The last 30 years in Boise City averaged 0.9° warmer than the 1900s. The biggest change is in January (+2.1°).
A smaller shift than in 84% of U.S. towns.
Change by month
The two periods overlap (1991–2000 is in both), which makes the gap a little smaller than it would be between separate periods. In a city of 238,000 people, part of the change is the city itself: pavement and buildings hold heat (the urban heat island).
How Boise City compares
Against 12,954 U.S. towns of 2,500 or more (one per 5 km climate cell), with Boise City’s place among Idaho’s.
Boise City weather by month
Highs, lows and precipitation from NOAA’s grid at Boise City’s center; snow, wet days and snow on the ground from Boise Air Terminal, ID. 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" | 0.0" | 8 | 0 | 53° – 65° |
| June | 82° | 51° | 0.8" | 0.0" | 5 | 0 | 62° – 75° |
| July | 93° | 59° | 0.2" | 0.0" | 2 | 0 | 65° – 82° |
| August | 91° | 57° | 0.2" | 0.0" | 2 | 0 | 68° – 77° |
| September | 81° | 48° | 0.4" | 0.0" | 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 |
How much a month can swing
A normal is an average. January swings the most: from 1991 to 2020 its average ranged from 20° to 38°. September is the most reliable, staying within 9°.
Where Boise City’s numbers come from
Normals are 30-year averages, not a forecast. How TownRatings reads climate data →
- Temperatures and precipitation: NOAA’s gridded 1991–2020 normals for the 5 km cell at Boise City’s center.
- Snow: Boise Air Terminal, ID (the official station).
- Frost, freezing nights, 90° and 100° days, heating and cooling: Boise Air Terminal, ID, 2.2 miles from the city’s center point, at about the same height; the city’s official station.
- Growing zone: USDA Plant Hardiness Zone Map, 2023. USDA Agricultural Research Service and PRISM Group, Oregon State University, prism.oregonstate.edu/phzm, accessed 8 Oct 2026.
- Then and now: NOAA’s gridded normals for 1901–2000 at the same cell.
- Storms and extremes: FEMA National Risk Index (expected annual losses to buildings).
Common questions about Boise City’s climate
What is the weather like in Boise City?
A typical July afternoon reaches 93°, a January night drops to 24°, and about 18 inches of snow falls in a normal winter. Milder January nights than 59% of U.S. towns; hotter July afternoons than 91% of U.S. towns.
How cold does it get in Boise City in winter?
January nights average 24°. About 108 nights a year reach 32° or below. In the coldest January of the last 30 years the month averaged 20°.
How much snow does Boise City get?
About 18 inches in a normal winter at Boise Air Terminal, ID, most of it in January and December, with snow on the ground about 17 days a year.
How hot does it get in Boise City?
July, with a typical high of 93° and a low of 59°. About 55 days a year reach 90° and 9 reach 100° (Boise Air Terminal, ID).
When is the first and last frost in Boise City?
In half of years the last spring frost (32°) comes by April 24 and the first fall frost by October 21, about 179 frost-free days, at Boise Air Terminal, ID.
What growing zone is Boise City in?
Zone 7a on the 2023 USDA Plant Hardiness Zone Map: the coldest night of a typical winter reaches about 5°.
What is the best time of year to visit Boise City?
By one simple rule (highs of 62–84° and lows of 40° or more), May, June and September. The rule is ours, not NOAA’s; the month table has the numbers to judge by.
Is Boise City getting warmer?
Yes: 1991–2020 averaged 0.9° warmer than 1901–2000 on NOAA’s grid. A smaller shift than 84% of U.S. towns.
Neighbors talk weather
Gardens, snow, and the best days of the year in Boise City.
Source: NOAA NCEI U.S. Climate Normals, 1991–2020 and 1901–2000; USDA/PRISM 2023 hardiness zones; FEMA National Risk Index. Today’s forecast: National Weather Service.