Climateby Month

Boise, ID climate by month

NOAA 1991-2020 normals · 2,700 ft elevation · also covers Meridian, Nampa

Summers in Boise are hot; winters are cold. Highs peak at 93°F in July and fall to 39°F in January. The wettest month is December (about 12 wet days) and the driest is August (about 2). Normal snowfall is about 18 in a year. The most comfortable time to visit is May.

Warmest month
93°F
July normal high
Coldest month
25°F
December normal low
Wet days a year
89
11.5 in of precipitation
Snow a year
17.6 in
normal snowfall

How warm is Boise?

Normal highs range from 39°F in January to 93°F in July.

20°40°60°80°100° January: normal high 39°F (4°C), low 26°F (-3°C) 39° 26° February: normal high 46°F (8°C), low 29°F (-2°C) March: normal high 56°F (13°C), low 35°F (2°C) April: normal high 62°F (17°C), low 40°F (4°C) May: normal high 72°F (22°C), low 48°F (9°C) June: normal high 81°F (27°C), low 54°F (12°C) July: normal high 93°F (34°C), low 62°F (17°C) 93° 62° August: normal high 91°F (33°C), low 61°F (16°C) September: normal high 80°F (27°C), low 53°F (12°C) October: normal high 65°F (18°C), low 42°F (6°C) November: normal high 49°F (9°C), low 32°F (0°C) December: normal high 39°F (4°C), low 25°F (-4°C) JFMAMJJASOND

Bars run from the normal low to the normal high for each month.

How rainy is Boise?

December has the most wet days (about 12); the year brings about 12 in of precipitation.

January: 11 wet days February: 9 wet days March: 10 wet days April: 9 wet days May: 8 wet days June: 5 wet days July: 2 wet days August: 2 wet days 2 September: 4 wet days October: 6 wet days November: 10 wet days December: 12 wet days 12 JFMAMJJASOND

Wet day: at least 0.01 in of rain or melted snow, counted from daily records 1991-2020.

How much does it snow?

Normal snowfall is 17.6 in a year, most of it in December.

January: 5.3 in of snow February: 3.3 in of snow March: 1.2 in of snow April: 0.1 in of snow May: 0.0 in of snow 0.0 June: 0.0 in of snow July: 0.0 in of snow August: 0.0 in of snow September: 0.0 in of snow October: 0.1 in of snow November: 2.0 in of snow December: 5.6 in of snow 5.6 JFMAMJJASOND

How humid is Boise?

Muggy days (dew point 65°F or higher) are rare in any month.

January: 0 muggy days 0 February: 0 muggy days March: 0 muggy days April: 0 muggy days May: 0 muggy days June: 0 muggy days July: 0 muggy days August: 0 muggy days September: 0 muggy days October: 0 muggy days November: 0 muggy days December: 0 muggy days JFMAMJJASOND

Muggy day: daily mean dew point of 65°F or higher, from hourly observations 1991-2020 at Boise Air Terminal/Gowen Fd Airport, 3.7 mi SSW of the city center.

How much daylight?

Daylight ranges from about 9.0 hours in December to 15.4 hours in June.

January: 9.4 hours of daylight February: 10.5 hours of daylight March: 11.9 hours of daylight April: 13.4 hours of daylight May: 14.7 hours of daylight June: 15.4 hours of daylight 15.4 July: 15.1 hours of daylight August: 13.9 hours of daylight September: 12.5 hours of daylight October: 11.0 hours of daylight November: 9.7 hours of daylight December: 9.0 hours of daylight 9.0 JFMAMJJASOND
See all numbers
Monthly climate normals and day counts for Boise, 1991-2020
MonthHighLowPrecip.Wet daysSnowMuggy daysDaylight
January 39°F26°F 1.4 in11 5.3 in 0 9.4 h
February 46°F29°F 1.0 in9 3.3 in 0 10.5 h
March 56°F35°F 1.3 in10 1.2 in 0 11.9 h
April 62°F40°F 1.2 in9 0.1 in 0 13.4 h
May 72°F48°F 1.4 in8 0.0 in 0 14.7 h
June 81°F54°F 0.8 in5 0.0 in 0 15.4 h
July 93°F62°F 0.2 in2 0.0 in 0 15.1 h
August 91°F61°F 0.2 in2 0.0 in 0 13.9 h
September 80°F53°F 0.4 in4 0.0 in 0 12.5 h
October 65°F42°F 0.8 in6 0.1 in 0 11.0 h
November 49°F32°F 1.2 in10 2.0 in 0 9.7 h
December 39°F25°F 1.5 in12 5.6 in 0 9.0 h

High and low: NOAA 1991-2020 normal daily high and low. Wet days: at least 0.01 in of rain or melted snow. Muggy days: daily mean dew point 65°F or higher.

Best months to visit Boise

By our comfort score, the best month is May.

Comfort score by month (0-100) and its parts, in days per month
MonthScoreComfortableNotable rainHot or cold
Jan 310517
Feb 41047
Mar 54451
Apr 661040
May 761641
Jun 701227
Jul 482122
Aug 483020
Sep 661315
Oct 651321
Nov 42145
Dec 300518

Score = 40 × share of comfortable days + 25 × share of days without notable rain + 20 × share of days neither hot (90°F+) nor cold (high 40°F or below) + 15 × daylight. How the score works.

Frost dates in Boise

The last spring frost typically comes around Apr 24, and the first fall frost around Oct 21, leaving 179 frost-free days in a typical year.

Frost and freeze dates for Boise
Typical date1 year in 10
Last spring frost (32°F)Apr 24after May 9
First fall frost (32°F)Oct 21before Oct 5
Last hard freeze (28°F)Apr 2after Apr 25
First hard freeze (28°F)Oct 31before Oct 17
Frost-free season179 daysunder 156 days

"Typical" is the date with a 50% chance of a later spring frost (or earlier fall frost). Planting after the "1 year in 10" spring date gives a 90% chance of no further frost. The Old Farmer's Almanac publishes 30% dates, which fall between our typical and 1-in-10 dates.

Station: Boise Air Terminal (USW00024131), NOAA 1991-2020 freeze probabilities. Frost dates for every city in Idaho.

Hottest and coldest readings, 1991-2020

The highest reading was 110°F (June 28, 2015); the lowest was -12°F (January 5, 1991).

From the temperature station's daily records with NOAA quality flags removed. Not an all-time record.

Near Boise

Similar climates elsewhere

Also covers

Meridian and Nampa use the same temperature and rain stations as Boise, so their monthly numbers are the ones on this page.

Where the numbers come from

  • Temperature, rain, snowfall, snow depth, frost dates, humidity and wind by hour and cloud cover: Boise Air Terminal (USW00024131), 3.7 mi SSW of the city center, 2,814 ft (114 ft higher than the city). NOAA normals and daily records, 1991-2020.
  • Daily humidity and wind: Boise Air Terminal/Gowen Fd Airport (726810-24131), 3.7 mi SSW of the city center, 2,823 ft (123 ft higher than the city). Hourly observations, 1991-2020.

Distances from the city center (USGS). Methodology · Report an error