Boise Temperatures: Averages by Month





The numbers here tell you how hot and cold the weather usually is in Boise, Idaho during each month of the year.

The average high and low temperatures are listed below monthly and annually for the city, in both degrees Fahrenheit and Celsius.

Maximums and minimums are only part of the temperature picture. To fill in the rest, there's information on how many days a month get above or below a given temperature.

To find out how often it rises over 70, 80 or 90 °F each month in Boise, scroll down farther. There are also monthly and yearly counts of days with cold weather.

The first set of high and low temperatures are averages for 2010 to 2019. Everything else here is based on 1991 to 2020 weather.

10-year temperature averages for Boise, 2010 to 2019
High °F Low °F   High °C Low °C
38 24 January 4 -4
46 30 February 8 -1
56 36 March 13 2
63 40 April 17 4
72 47 May 22 8
82 55 June 28 13
94 63 July 34 17
92 62 August 33 17
80 54 September 27 12
65 42 October 18 6
50 32 November 10 0
38 25 December 4 -4
65 43 Year 18 6
30-year temperature averages for Boise, 1991 to 2020
High °F Low °F   High °C Low °C
39 26 January 4 -4
46 29 February 8 -2
56 35 March 13 2
62 40 April 17 4
72 48 May 22 9
81 54 June 27 12
93 62 July 34 17
91 61 August 33 16
80 53 September 27 11
65 42 October 18 5
49 32 November 9 0
39 25 December 4 -4
64 42 Year 18 6

Days of Hot Weather in Boise

About half of summer days at Boise see the temperature climb into the 90s Fahrenheit. The 90-degree weather can show up here as early as April and last until October. Highs in the 100s occur during June, July and August, amounting to six days a year on average.

Number of days in Boise of at least 70, 80 or 90 °F
  70 °F
21 °C
80 °F
27 °C
90 °F
32 °C
January 0 0 0
February 0 0 0
March 2 0 0
April 7 1 0
May 18 8 1
June 26 17 7
July 31 29 22
August 31 29 20
September 25 16 5
October 9 3 0
November 0 0 0
December 0 0 0
Year 149 103 55

How Often Boise Has Cold Temperatures

Freezing temperatures can happen in Boise anytime from September until May. Boise typically has 108 frosty nights a year. The coldest nights drop down to below 0 °F (-18 °C). It normally only gets that cold here one or two times a year, usually in December and January.

On an average of 16 days annually the thermometer never rises above freezing. Days that chilly show up during November to March.

Days per month on average in Boise when the minimum temperature drops to 32, 20 or 10 °F or below
  10 °F
-12 °C
20 °F
-8 °C
32 °F
0 °C
January 2 8 26
February 0 3 20
March 0 0 11
April 0 0 5
May 0 0 1
June 0 0 0
July 0 0 0
August 0 0 0
September 0 0 0
October 0 0 4
November 1 3 16
December 1 9 25
Year 4 23 108
References

Jay Lawrimore, Ron Ray, Scott Applequist, Bryant Korzeniewski, Matthew Menne. 2016. Global Summary of the Month and Year, Version 1.0. NOAA National Centers for Environmental Information.

NOAA National Centers for Environmental Information (NCEI). Climate Normals.

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