| 2023 Hardiness Zone: | Zone 6a: -10°F to -5°F Zone 5a: -20°F to -15°F Zone 5b: -15°F to -10°F | |
| 2012 Hardiness Zone: | Zone 5a: -20°F to -15°F Zone 4b: -25°F to -20°F Zone 5b: -15°F to -10°F | |
| 1990 Hardiness Zone: | Zone 4b: -25F to -20F | |
| Average First Frost Date: | Sep.1 - Sep. 10 | |
| Average Last Frost Date: | May 21 - May 31 | |
| Koppen-Geiger Climate Zone: | Dfb - Humid Continental Mild Summer, Wet All Year | |
| Ecoregion: | 17s - Bitterroot-Frenchtown Valley | |
| Current Drought Status: | Exceptional Drought | |
| Heat Zone Days: | 8 - 14 days Over 86°F |
Annual Climate Data for ZIP Code 59840 - Hamilton, MT | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | Annual |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Avg Min Temp (°F) | 17 | 20 | 26 | 32 | 38 | 44 | 48 | 47 | 40 | 31 | 23 | 17 | 32 |
| Avg Max Temp (°F) | 34 | 41 | 50 | 58 | 67 | 75 | 83 | 82 | 71 | 59 | 42 | 34 | 58 |
| Avg Precip (In.) | 1.03 | .79 | .86 | 1.03 | 1.69 | 1.58 | 1.01 | 1.15 | 1.06 | .71 | 1.03 | 1.04 | 12.97 |