September for balanced conditions; late July for peak summer weather. September combines manageable crowds, fall foliage, elk rut in Yellowstone, and lodging prices 30–40% below summer peak. Late July offers the warmest, clearest weather (avg high 75°F, 77% clear skies) but with maximum crowds. Winter (November–March) is prime for snowmobiling and Nordic skiing, with 400+ inches of annual snowfall
| Month | High (°F) | Low (°F) | Notes |
|---|---|---|---|
| Jan | 23 | 9 | cold & changeable |
| Feb | 26 | 11 | cold & changeable |
| Mar | 36 | 18 | crisp & changeable |
| Apr | 43 | 23 | crisp & changeable |
| May | 53 | 30 | cool & changeable |
| Jun | 66 | 40 | mild & changeable |
| Jul | 78 | 49 | warm & mostly dry |
| Aug | 76 | 48 | warm & mostly dry |
| Sep | 66 | 40 | mild & mostly dry |
| Oct | 48 | 28 | cool & changeable |
| Nov | 32 | 15 | crisp & changeable |
| Dec | 22 | 8 | cold & changeable |