Rapid City, SD weather in August
August in Rapid City: warm, with some rain. Highs 85°F, lows 56°F, about 8 days with rain. This is the peak of the warm season in Rapid City.
- Normal high
- 85°F
- Normal low
- 56°F
- Wet days
- 8
- 1.6 in total
- Muggy days
- 0
- dew point 65°F+
How August changes from start to finish
| August 1 | August 31 | |
|---|---|---|
| Normal high | 88°F | 82°F |
| Normal low | 59°F | 52°F |
| Chance of a wet day | 29% | 23% |
| Sunrise / sunset | 5:41 am / 8:17 pm | 6:15 am / 7:31 pm |
| Daylight | 14.6 h | 13.3 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 am62°Fdew point 52°F
- 9 am74°Fdew point 53°F
- Noon81°Fdew point 52°F
- 3 pm83°Fdew point 51°F
- 6 pm79°Fdew point 52°F
- 9 pm69°Fdew point 53°F
NOAA hourly normals (local standard time) from Ellsworth AFB (8 mi away); average wind 9 mph; clear or few clouds in 60% of daytime hours, mostly cloudy or overcast in 27%.
What kind of days to expect
- Comfortable dayshigh 65-80°F and dew point under 60°F6 of 31
- Hot dayshigh 90°F or more11 of 31
- Muggy daysdaily mean dew point 65°F or more0 of 31
- Wet daysat least 0.01 in of rain or melted snow8 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 1.6 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, 1991-20202003: average high 92°F
- Coolest August2019: average high 80°F
- Wettest August2014: 4.0 in
- Driest August1995: 0.5 in
- Highest reading107°F (August 29, 2012)
- Lowest reading37°F (August 31, 2020)
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 | 86°F | 85°F | 76°F |
| Normal low | 59°F | 56°F | 46°F |
| Wet days | 10 | 8 | 7 |
| Comfortable days | 6 | 6 | 12 |
| Daylight | 15.1 h | 14.0 h | 12.5 h |
Highs change by -1°F from July and -9°F into September.
Nearby alternatives in August
- Cooler: Keystone, SD16 mi · high 78°F · 9 wet days
How Rapid City ranks in August
- Normal high200th warmest of 378 cities; 1st of 4 in South Dakota
- Wet days153rd driest of 378
- Comfortable days115th most of 341
What to pack for Rapid City in August
- Light, breathable clothing – highs near 85°F
- Layers – afternoons near 85°F but nights near 56°F
Heating and cooling
August has 25 heating degree days and 205 cooling degree days (base 65°F), 3% of the year's total heating and cooling demand.
Questions
How hot is Rapid City in August?
The normal high is 85°F and the normal low is 56°F. From 1991 to 2020 the hottest August reading was 107°F (most recently on August 29, 2012).
Does it rain a lot in Rapid City in August?
About 8 days in August have at least 0.01 in of precipitation, and the normal total is 1.6 in. The wettest August in 1991-2020 was in 2014 (4.0 in); the driest was in 1995 (0.5 in).
Is August a good time to visit Rapid City?
August ranks 7th of 12 months on our comfort score for Rapid City (55 out of 100). It has about 6 comfortable days and about 11 days at 90°F or hotter. The best months are May and June.
Where the numbers come from
- Temperature and rain: Rapid City Rgnl Airport (USW00024090), 9.2 mi ESE of the city center, 3,160 ft (83 ft lower than the city). NOAA normals and daily records, 1991-2020.
- Snowfall, snow depth and frost dates: Rapid City WFO (USC00396948), 1.1 mi ESE of the city center, 3,379 ft (136 ft higher than the city). NOAA normals and daily records, 1991-2020.
- Humidity and wind by hour and cloud cover: Ellsworth AFB (USW00024006), 8.1 mi NE of the city center, 3,215 ft . NOAA normals and daily records, 1991-2020.
- Daily humidity and wind: Rapid City Regional Airport (726620-24090), 9.1 mi ESE of the city center, 3,162 ft (81 ft lower than the city). Hourly observations, 1991-2020.