Boulder Temperatures: Averages by Month





The numbers here tell you how hot and cold the weather usually is in Boulder, Colorado 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 Boulder, 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 recorded at an elevation of 5,486 feet (1,672 metres).

10-year temperature averages for Boulder, 2010 to 2019
High °F Low °F   High °C Low °C
48 22 January 9 -6
44 18 February 7 -8
50 24 March 10 -4
64 36 April 18 2
64 39 May 18 4
80 50 June 26 10
89 57 July 32 14
90 58 August 32 14
85 51 September 29 10
61 31 October 16 -1
52 26 November 11 -3
47 24 December 8 -4
66 38 Year 19 3
30-year temperature averages for Boulder, 1991 to 2020
High °F Low °F   High °C Low °C
47 22 January 8 -6
48 22 February 9 -5
57 29 March 14 -2
63 35 April 17 1
71 43 May 22 6
83 51 June 28 11
88 57 July 31 14
86 56 August 30 13
79 48 September 26 9
66 37 October 19 3
55 28 November 13 -2
46 21 December 8 -6
66 37 Year 19 3

Days of Hot Weather in Boulder

About one-third of summer days at Boulder have highs in the 90s Fahrenheit. But it's uncommon for the temperature to get any hotter. Just once a year on average the city has a day of 100-degree weather. A day that hot can show up in June or July.

Days per month in Boulder 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 1 0 0
March 4 0 0
April 9 1 0
May 19 7 1
June 28 20 6
July 31 28 14
August 30 27 10
September 26 15 3
October 13 4 0
November 3 0 0
December 0 0 0
Year 163 101 33

How Often Boulder Has Cold Temperatures

Most winter nights at Boulder have freezing temeratures and a handful of those are bitterly cold. The city averages four nights a winter when the thermometer plummets to 0 °F (-18 °C) or below. December, January and February are the months most likely to have a night that cold. November and March are also capable of dropping down to zero Fahrenheit.

Boulder averages 13 days a year that remain below freezing all day long. A frosty day can appear any time from October to April.

Days per month on average in Boulder 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 4 12 27
February 3 11 23
March 1 4 20
April 0 1 11
May 0 0 2
June 0 0 0
July 0 0 0
August 0 0 0
September 0 0 1
October 0 1 8
November 1 6 20
December 4 13 27
Year 14 48 138
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.

Colorado Temperatures
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