Late June to early September; or September for fewer crowds. Late June–early September offers the warmest temperatures (avg highs 78–87°F), long daylight hours, and full access to all parks and outdoor activities. September offers fall foliage in Spearfish Canyon, manageable crowds, and comfortable hiking weather after the Sturgis Rally peak
| Month | High (°F) | Low (°F) | Notes |
|---|---|---|---|
| Jan | 38 | 20 | crisp & sunny |
| Feb | 38 | 18 | crisp & mostly dry |
| Mar | 50 | 28 | cool & mostly dry |
| Apr | 58 | 35 | cool & changeable |
| May | 67 | 46 | mild & changeable |
| Jun | 79 | 56 | warm & changeable |
| Jul | 87 | 64 | hot & changeable |
| Aug | 85 | 61 | warm & changeable |
| Sep | 77 | 54 | warm & mostly dry |
| Oct | 61 | 40 | mild & mostly dry |
| Nov | 49 | 30 | cool & sunny |
| Dec | 37 | 20 | crisp & mostly dry |