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).
| 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 |
| 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.
| 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.
| 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.