| 2023 Hardiness Zone: | Zone 5a: -20°F to -15°F Zone 5b: -15°F to -10°F Zone 4b: -25°F to -20°F Zone 4a: -30°F to -25°F |
| 2012 Hardiness Zone: | Zone 3b: -35°F to -30°F Zone 4b: -25°F to -20°F Zone 5a: -20°F to -15°F Zone 4a: -30°F to -25°F |
| 1990 Hardiness Zone: | Zone 4a: -30F to -25F |
| Average First Frost Date: | Sep. 21 - Sep. 30 |
| Average Last Frost Date: | May 21 - May 31 |
| Koppen-Geiger Climate Zone: | BSk - Cold Semi-Arid Climate |
| Ecoregion: | 43n - Central Grassland |
| Heat Zone Days: | 46 - 60 days Over 86°F |
Annual Climate Data for ZIP Code 59327 - Forsyth, MT | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | Annual |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Avg Min Temp (°F) | 8 | 14 | 23 | 33 | 43 | 51 | 56 | 55 | 44 | 33 | 21 | 11 | 33 |
| Avg Max Temp (°F) | 33 | 40 | 50 | 62 | 71 | 81 | 89 | 87 | 76 | 63 | 45 | 35 | 61 |
| Avg Precip (In.) | .52 | .37 | .75 | 1.32 | 2.37 | 2.2 | 1.43 | .95 | 1.28 | 1.18 | .61 | .49 | 13.46 |