Keystone, SD weather in August
Keystone is mild in August, with some rain: highs average 78°F and nights drop to about 49°F. Expect about 9 wet days. This is the peak of the warm season in Keystone. A great month for outdoor plans.
- Normal high
- 78°F
- Normal low
- 49°F
- Wet days
- 9
- 2.4 in total
- Muggy days
- 0
- dew point 65°F+
How August changes from start to finish
| August 1 | August 31 | |
|---|---|---|
| Normal high | 80°F | 75°F |
| Normal low | 52°F | 45°F |
| Chance of a wet day | 35% | 26% |
| Sunrise / sunset | 5:42 am / 8:17 pm | 6:16 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 am56°Fdew point 46°F
- 9 am70°Fdew point 47°F
- Noon74°Fdew point 46°F
- 3 pm75°Fdew point 46°F
- 6 pm70°Fdew point 46°F
- 9 pm61°Fdew point 47°F
NOAA hourly normals (local standard time) from Custer Co Airport (15 mi away); average wind 6 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°F15 of 31
- Hot dayshigh 90°F or more2 of 31
- Muggy daysdaily mean dew point 65°F or more0 of 31
- Wet daysat least 0.01 in of rain or melted snow9 of 31
- Notable rainat least 0.10 in5 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 2.4 in; a dry August brings about 1.6 in and a wet one about 3.1 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 83°F
- Coolest August1992: average high 72°F
- Wettest August1999: 4.5 in
- Driest August1994: 0.8 in
- Highest reading98°F (August 30, 2012)
- Lowest reading30°F (August 17, 2002)
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 | 79°F | 78°F | 69°F |
| Normal low | 51°F | 49°F | 40°F |
| Wet days | 12 | 9 | 7 |
| Comfortable days | 13 | 15 | 15 |
| Daylight | 15.1 h | 13.9 h | 12.5 h |
Highs change by -1°F from July and -9°F into September.
Nearby alternatives in August
- Warmer: Rapid City, SD16 mi · high 85°F · 8 wet days
- Drier: Casper, WY162 mi · high 87°F · 6 wet days
How Keystone ranks in August
- Normal high332nd warmest of 378 cities; 4th of 4 in South Dakota
- Wet days208th driest of 378
- Comfortable days30th most of 341
What to pack for Keystone in August
- Layers – afternoons near 78°F but nights near 49°F
- A rain jacket or umbrella – rain on about 9 days
Heating and cooling
August has 103 heating degree days and 50 cooling degree days (base 65°F), 2% of the year's total heating and cooling demand.
Questions
How hot is Keystone in August?
The normal high is 78°F and the normal low is 49°F. From 1991 to 2020 the hottest August reading was 98°F (most recently on August 30, 2012).
Does it rain a lot in Keystone in August?
About 9 days in August have at least 0.01 in of precipitation, and the normal total is 2.4 in. The wettest August in 1991-2020 was in 1999 (4.5 in); the driest was in 1994 (0.9 in).
Is August a good time to visit Keystone?
August ranks 2nd of 12 months on our comfort score for Keystone (71 out of 100). It has about 15 comfortable days and about 2 days at 90°F or hotter. The best month is June.
Where the numbers come from
- Temperature, rain, snowfall, snow depth and frost dates: Pactola Dam (USC00396427), 12 mi NNW of the city center, 4,720 ft (385 ft higher than the city). NOAA normals and daily records, 1991-2020.
- Humidity and wind by hour: Custer Co Airport (USW00094032), 15 mi SW of the city center, 5,545 ft (1,210 ft higher than the city). NOAA normals and daily records, 1991-2020.
- Cloud cover: Ellsworth AFB (USW00024006), 24 mi NE of the city center, 3,215 ft (1,120 ft lower than the city). NOAA normals and daily records, 1991-2020.
- Daily humidity and wind: Rapid City Regional Airport (726620-24090), 21 mi ENE of the city center, 3,162 ft (1,173 ft lower than the city). Hourly observations, 1991-2020.