Climate averages 1991–2020
Boulder weather
in July.
A hot, moderately wet month: the warmest and the 9th driest of the year.
Long-term climate patterns, not a forecast for a particular trip.
July is a hot month in Boulder: daytime highs average 28.7°C and nights cool to about 14.4°C. By daytime temperature it is the warmest month of the year.
Expect about 75 mm of rain on roughly 15 days, which makes July a moderately wet month (the 9th driest of the 12 months). Daylight, from sunrise to sunset, lasts about 14 h 43 min on an average July day.
The nearest other city in this atlas is Longmont (22 km away). In July its highs average 29.5°C, 0.8°C warmer than Boulder, with 42 mm of rain.
Among the 498 cities listed in the United States, Boulder ranks joint 323rd of 498 for the warmest July highs and joint 235th of 498 for the driest July (rainfall, lowest first). The mean July high of those 498 cities is 30.3°C; Boulder is 1.6°C cooler than that mean.
From July to August, average highs fall by 1.2°C to 27.5°C, and monthly rainfall falls from 75 mm to 71 mm.
The annual picture
July in context
Monthly rainfall
Average total · mmAverages from hourly ERA5 reanalysis data. Actual weather varies from year to year. How these numbers are calculated
Every month, side by side
Boulder climate table
| Month | Average highHigh / low | Average low | Rainfall mm/month | Rain days ≥1 mm/day | Daylight hours/dayDaylight h/day |
|---|---|---|---|---|---|
| January | 4.2°C-8.7°C | -8.7°C | 24 | 5.7 | 9.710 h |
| February | 5.4°C-8.3°C | -8.3°C | 26 | 6.7 | 10.711 h |
| March | 10.0°C-4.5°C | -4.5°C | 50 | 8.8 | 11.912 h |
| April | 13.7°C-0.4°C | -0.4°C | 78 | 11.1 | 13.213 h |
| May | 19.2°C5.1°C | 5.1°C | 103 | 14.9 | 14.414 h |
| June | 25.6°C10.8°C | 10.8°C | 77 | 14.2 | 15.015 h |
| July, selected | 28.7°C14.4°C | 14.4°C | 75 | 14.8 | 14.715 h |
| August | 27.5°C13.7°C | 13.7°C | 71 | 14.8 | 13.814 h |
| September | 23.7°C9.5°C | 9.5°C | 54 | 9.6 | 12.512 h |
| October | 16.5°C3.1°C | 3.1°C | 48 | 7.4 | 11.211 h |
| November | 9.1°C-3.9°C | -3.9°C | 32 | 6.4 | 10.010 h |
| December | 4.0°C-8.8°C | -8.8°C | 23 | 5.3 | 9.49 h |
Rainfall is the average of the 30 separate monthly totals. A rain day is a local calendar day with at least 1 mm of precipitation. Daylight is the calculated sunrise-to-sunset length, not measured sunshine.
Compare places
July in nearby cities
- Longmont in JulyUnited States · 22 kmHigh 29.5°C · Low 15.0°C · 42 mm rain
- Westminster (Colorado), United States in JulyUnited States · 28 kmHigh 29.3°C · Low 14.5°C · 41 mm rain
- Arvada in JulyUnited States · 28 kmHigh 29.1°C · Low 14.4°C · 41 mm rain
- Thornton in JulyUnited States · 30 kmHigh 29.2°C · Low 14.5°C · 41 mm rain
- Lakewood in JulyUnited States · 38 kmHigh 29.2°C · Low 14.4°C · 41 mm rain
- Denver in JulyUnited States · 39 kmHigh 29.4°C · Low 14.6°C · 41 mm rain
- Loveland in JulyUnited States · 46 kmHigh 29.2°C · Low 14.7°C · 44 mm rain
- Aurora (Colorado), United States in JulyUnited States · 49 kmHigh 30.4°C · Low 16.0°C · 38 mm rain
Read the numbers correctly
Climate, not a promise.
These patterns help compare months. They cannot tell you the weather on a specific day of your trip.
Sources, method and limitsHow these numbers are made (what the highs, lows and rain days mean, the sources and the model cell used for Boulder) is explained once on the Boulder year overview and on the Sources, method and limits page.