Climate averages 1991–2020
Boulder weather
in April.
A cool, moderately wet month: the 7th warmest and the 11th driest of the year.
Long-term climate patterns, not a forecast for a particular trip.
April is a cool month in Boulder: daytime highs average 13.7°C and nights cool to about -0.4°C. By daytime temperature it is the 7th warmest of the 12 months.
Expect about 78 mm of rain on roughly 11 days, which makes April a moderately wet month (the 11th driest of the 12 months). Daylight, from sunrise to sunset, lasts about 13 h 14 min on an average April day.
The nearest other city in this atlas is Longmont (22 km away). In April its highs average 14.8°C, 1.2°C warmer than Boulder, with 67 mm of rain.
Among the 498 cities listed in the United States, Boulder ranks joint 413th of 498 for the warmest April highs and joint 218th of 498 for the driest April (rainfall, lowest first). The mean April high of those 498 cities is 19.4°C; Boulder is 5.7°C cooler than that mean.
From April to May, average highs rise by 5.5°C to 19.2°C, and monthly rainfall rises from 78 mm to 103 mm.
The annual picture
April 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, selected | 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 | 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
April in nearby cities
- Longmont in AprilUnited States · 22 kmHigh 14.8°C · Low 0.4°C · 67 mm rain
- Westminster (Colorado), United States in AprilUnited States · 28 kmHigh 14.4°C · Low -0.5°C · 70 mm rain
- Arvada in AprilUnited States · 28 kmHigh 14.4°C · Low -0.6°C · 70 mm rain
- Thornton in AprilUnited States · 30 kmHigh 14.4°C · Low -0.4°C · 70 mm rain
- Lakewood in AprilUnited States · 38 kmHigh 14.2°C · Low -0.6°C · 70 mm rain
- Denver in AprilUnited States · 39 kmHigh 14.4°C · Low -0.5°C · 70 mm rain
- Loveland in AprilUnited States · 46 kmHigh 14.7°C · Low 0.2°C · 64 mm rain
- Aurora (Colorado), United States in AprilUnited States · 49 kmHigh 15.3°C · Low 0.9°C · 55 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.