Rapid City weather in August: Rapid City, South Dakota: normal highs, lows, rain and records for August
Rapid City in August has a normal high of 85°F and a normal low of 56°F, a daily mean of 71°F, falling from 88°F on the 1st to 82°F by the 31st. Measurable precipitation falls on 8 days in a normal August, 1.59 inches in all. (NOAA 1991-2020 normals)
In metric: a normal high of 30°C and low of 13°C, 40 mm of precipitation in August.
- NOAA stationRapid City Regional Airport
- Station IDUSW00024090
- Location44.04°N 103.05°W
- Elevation3,160 ft (963 m)
- Population79,894
- Jan 36° 13°
- Feb 38° 14°
- Mar 48° 23°
- Apr 57° 31°
- May 67° 42°
- Jun 78° 52°
- Jul 86° 59°
- Aug 85° 56°
- Sep 76° 46°
- Oct 60° 34°
- Nov 47° 22°
- Dec 37° 14°
Each month: normal high (large) and low, °F. Fill: the month's normal mean, colder blue to hotter red.
How warm is Rapid City in August?
The normal high is 85°F and the normal low 56°F, for a daily mean of 70.8°F. August is 1.6°F cooler than July and 9.5°F warmer than September. August is the 2nd warmest month of the year in Rapid City and the 5th wettest. Across the month the normal high falls 6°F, from 88°F on August 1 to 82°F on August 31. From one year to the next August's mean temperature typically moves about 2.6°F either way (NOAA's standard deviation), so roughly two Augusts in three average between 68°F and 73°F.
Bars above: each day's normal high to low. Columns below: the chance of 0.01 inch or more of precipitation that day, on a scale of 0 to 100% (highest 29%).
| Day | High | Low | Chance of 0.01 in | Chance of 0.10 in |
|---|---|---|---|---|
| August 1 | 88°F | 59°F | 29% | 14% |
| August 8 | 87°F | 58°F | 28% | 13% |
| August 15 | 86°F | 57°F | 26% | 12% |
| August 22 | 85°F | 55°F | 24% | 11% |
| August 31 | 82°F | 52°F | 23% | 10% |
Every day of August: normal high, low and chance of precipitation (warmest afternoon August 1, coldest night August 31)
| Day | High | Low | Chance of 0.01 in | Chance of 0.10 in | Daylight |
|---|---|---|---|---|---|
| August 1 | 88°F | 59°F | 29% | 14% | 14 h 40 min |
| August 2 | 88°F | 59°F | 29% | 14% | 14 h 40 min |
| August 3 | 88°F | 59°F | 29% | 14% | 14 h 30 min |
| August 4 | 87°F | 59°F | 29% | 14% | 14 h 30 min |
| August 5 | 87°F | 59°F | 28% | 14% | 14 h 30 min |
| August 6 | 87°F | 59°F | 28% | 14% | 14 h 30 min |
| August 7 | 87°F | 59°F | 28% | 14% | 14 h 20 min |
| August 8 | 87°F | 58°F | 28% | 13% | 14 h 20 min |
| August 9 | 87°F | 58°F | 28% | 13% | 14 h 20 min |
| August 10 | 87°F | 58°F | 27% | 13% | 14 h 20 min |
| August 11 | 87°F | 58°F | 27% | 13% | 14 h 10 min |
| August 12 | 86°F | 58°F | 27% | 13% | 14 h 10 min |
| August 13 | 86°F | 57°F | 27% | 13% | 14 h 10 min |
| August 14 | 86°F | 57°F | 26% | 12% | 14 h 10 min |
| August 15 | 86°F | 57°F | 26% | 12% | 14 h |
| August 16 | 86°F | 57°F | 26% | 12% | 14 h |
| August 17 | 86°F | 56°F | 26% | 12% | 14 h |
| August 18 | 85°F | 56°F | 25% | 12% | 14 h |
| August 19 | 85°F | 56°F | 25% | 11% | 13 h 50 min |
| August 20 | 85°F | 55°F | 25% | 11% | 13 h 50 min |
| August 21 | 85°F | 55°F | 24% | 11% | 13 h 50 min |
| August 22 | 85°F | 55°F | 24% | 11% | 13 h 50 min |
| August 23 | 84°F | 55°F | 24% | 11% | 13 h 40 min |
| August 24 | 84°F | 54°F | 24% | 11% | 13 h 40 min |
| August 25 | 84°F | 54°F | 24% | 11% | 13 h 40 min |
| August 26 | 84°F | 54°F | 24% | 11% | 13 h 30 min |
| August 27 | 83°F | 53°F | 23% | 11% | 13 h 30 min |
| August 28 | 83°F | 53°F | 23% | 10% | 13 h 30 min |
| August 29 | 83°F | 53°F | 23% | 10% | 13 h 30 min |
| August 30 | 83°F | 52°F | 23% | 10% | 13 h 20 min |
| August 31 | 82°F | 52°F | 23% | 10% | 13 h 20 min |
- Normal high
- 85°FAugust average
- Normal low
- 56°FAugust average
- Precipitation
- 1.59 inmonth total
- Days with precipitation
- 80.01 inch or more
- Days at 90°F or more
- 11
- Daylight
- 14 h 40 min to 13 h 20 minAugust 1 to August 31
- Days at 70°F or more
- 30
- Days at 80°F or more
- 25
- Sunshine
- 86%of clear-sky sunlight (NASA)
Source: NOAA NCEI 1991-2020 daily normals, station USW00024090; monthly normals. Daylight is computed from the place's latitude with NOAA's solar equations.
Does it rain in Rapid City in August?
On a given August day the chance of 0.01 inch or more is 26% on average, highest around August 1 (29%). In all, 1.59 in falls on 8 days of a normal August.
In a normal August in Rapid City, 11 days reach 90°F.
Source: NOAA NCEI 1991-2020 daily and monthly normals, station USW00024090.
How humid and windy is Rapid City in August?
At 3 p.m. the normal temperature is 82°F with 30% relative humidity and a dew point of 47°F; at 6 a.m. it is 58°F with 69% humidity. The wind averages 9.5 mph, most often from the east in the afternoon. A dew point under 50°F feels dry.
| Time | Temperature | Dew point | Humidity | Wind | Clear or few clouds |
|---|---|---|---|---|---|
| 6 a.m. | 58°F | 48°F | 69% | 7.3 mph | 80% |
| 9 a.m. | 72°F | 50°F | 46% | 10.9 mph | 81% |
| noon | 80°F | 49°F | 34% | 12.8 mph | 83% |
| 3 p.m. | 82°F | 47°F | 30% | 12.4 mph | 83% |
| 6 p.m. | 75°F | 49°F | 40% | 9.8 mph | 86% |
| 9 p.m. | 64°F | 49°F | 57% | 7.4 mph | 85% |
Source: NOAA NCEI 1991-2020 hourly normals, station USW00024090. Hourly normals exist only for NOAA's first-order stations; a dash where NOAA publishes no value for that hour (the sky at some hours).
What are the records for August in Rapid City?
The warmest August temperature on Rapid City's official record (since 1942) is 107°F, on August 13, 2007; the coldest is 37°F, on August 31, 2020. The wettest August brought 4.83 in (1982); the snowiest, 1.0 inches (1950).
The August mean against the 1991-2020 normal of 70.8°F: 2021 71.5°F (+0.7), 2022 74.2°F (+3.4), 2023 71.3°F (+0.5), 2024 73.7°F (+2.9), 2025 72.5°F (+1.7), 2026 73.1°F (+2.3). 6 of 6 ran warmer than normal.
| August | Mean | Against normal | Precip. |
|---|---|---|---|
| 2021 | 71.5°F | +0.7°F | 2.14 in |
| 2022 | 74.2°F | +3.4°F | 2.76 in |
| 2023 | 71.3°F | +0.5°F | 0.87 in |
| 2024 | 73.7°F | +2.9°F | 0.97 in |
| 2025 | 72.5°F | +1.7°F | 2.96 in |
| 2026 | 73.1°F | +2.3°F | 2.17 in |
Source: records: ACIS, NWS threaded record RAPthr; recent months: ACIS, station USW00024090. Records and recent months use complete months only.
How does August in Rapid City compare across South Dakota?
Across the 100 places PlainClimate covers in South Dakota, August normal highs run from 78°F in Astoria to 91°F in Interior; Rapid City's is 85°F.
Source: NOAA NCEI 1991-2020 monthly normals for every station in the state.
Other months and places
- Rapid City in July86°F by day, 59°F at night
- Rapid City in September76°F by day, 46°F at night
- Rapid City through the yearEvery month, frost dates, records and recent years
- South Dakota in AugustThe statewide normal and the warmest and coolest places
- Interior: South Dakota's warmest Augustnormal high 91°F