Boulder, CO weather in August
Boulder is warm in August, with frequent rain: highs average 86°F and nights drop to about 56°F. Rain falls on about 11 days. This is the peak of the warm season in Boulder.
- Normal high
- 86°F
- Normal low
- 56°F
- Wet days
- 11
- 1.7 in total
- Muggy days
- 0
- dew point 65°F+
How August changes from start to finish
| August 1 | August 31 | |
|---|---|---|
| Normal high | 88°F | 84°F |
| Normal low | 58°F | 53°F |
| Chance of a wet day | 37% | 30% |
| Sunrise / sunset | 5:59 am / 8:15 pm | 6:28 am / 7:34 pm |
| Daylight | 14.3 h | 13.1 h |
Chance of a wet day: average for the first and last 7 days of the month. Times are local clock time (Mountain Time).
A typical August day
- 6 am61°Fdew point 49°F
- 9 am74°Fdew point 49°F
- Noon83°Fdew point 45°F
- 3 pm84°Fdew point 44°F
- 6 pm78°Fdew point 47°F
- 9 pm68°Fdew point 49°F
NOAA hourly normals (local standard time) from Denver Intl Airport (35 mi away); average wind 9 mph; clear or few clouds in 38% of daytime hours, mostly cloudy or overcast in 38%.
What kind of days to expect
- Comfortable dayshigh 65-80°F and dew point under 60°F5 of 31
- Hot dayshigh 90°F or more10 of 31
- Muggy daysdaily mean dew point 65°F or more0 of 31
- Wet daysat least 0.01 in of rain or melted snow11 of 31
- Notable rainat least 0.10 in4 of 31
- Freezing nightslow 32°F or below0 of 31
- Snow on the groundsnow depth 1 in or more0 of 31
Average days per August, counted from daily records for each year 1991-2020.
Rain in August
Normal precipitation is 1.7 in; a dry August brings about 0.8 in and a wet one about 2.0 in (25th and 75th percentiles). About 1 day brings half an inch or more.
How August varies from year to year
- Warmest August, 1991-20202011: average high 92°F
- Coolest August1992: average high 80°F
- Wettest August1999: 5.5 in
- Driest August2019: 0.1 in
- Highest reading100°F (August 16, 2002)
- Lowest reading40°F (August 28, 2004)
From the station's daily records with NOAA quality flags removed; most recent date shown when a reading repeats.
August compared with July and September
| July | August | September | |
|---|---|---|---|
| Normal high | 88°F | 86°F | 79°F |
| Normal low | 57°F | 56°F | 48°F |
| Wet days | 11 | 11 | 8 |
| Comfortable days | 3 | 5 | 13 |
| Daylight | 14.7 h | 13.7 h | 12.4 h |
Highs change by -2°F from July and -7°F into September.
Nearby alternatives in August
- Warmer: Moab, UT250 mi · high 96°F · 6 wet days
- Drier: Greeley, CO41 mi · high 89°F · 7 wet days
- Cooler: Estes Park, CO28 mi · high 78°F · 13 wet days
How Boulder ranks in August
- Normal high190th warmest of 378 cities; 6th of 17 in Colorado
- Wet days291st driest of 378
- Comfortable days136th most of 341
What to pack for Boulder in August
- Light, breathable clothing – highs near 86°F
- Layers – afternoons near 86°F but nights near 56°F
- A rain jacket or umbrella – rain on about 11 days
Heating and cooling
August has 12 heating degree days and 190 cooling degree days (base 65°F), 3% of the year's total heating and cooling demand.
Questions
How hot is Boulder in August?
The normal high is 86°F and the normal low is 56°F. From 1991 to 2020 the hottest August reading was 100°F (August 16, 2002).
Does it rain a lot in Boulder in August?
About 11 days in August have at least 0.01 in of precipitation, and the normal total is 1.7 in. The wettest August in 1991-2020 was in 1999 (5.5 in); the driest was in 2019 (0.1 in).
Is August a good time to visit Boulder?
August ranks 7th of 12 months on our comfort score for Boulder (54 out of 100). It has about 5 comfortable days and about 10 days at 90°F or hotter. The best month is May.
Where the numbers come from
- Temperature, rain, snowfall, snow depth and frost dates: Boulder (USC00050848), 1.6 mi S of the city center, 5,484 ft (165 ft higher than the city). NOAA normals and daily records, 1991-2020.
- Humidity and wind by hour: Denver Intl Airport (USW00003017), 35 mi ESE of the city center, 5,414 ft (95 ft higher than the city). NOAA normals and daily records, 1991-2020.
- Cloud cover: Aurora Buckley Fld ANGB (USW00023036), 35 mi SE of the city center, 5,663 ft (344 ft higher than the city). NOAA normals and daily records, 1991-2020.
- Daily humidity and wind: Denver International Airport (725650-03017), 35 mi ESE of the city center, 5,404 ft (85 ft higher than the city). Hourly observations, 1991-2020.