| 2023 Hardiness Zone: | Zone 5a: -20°F to -15°F Zone 4b: -25°F to -20°F Zone 4a: -30°F to -25°F | |
| 2012 Hardiness Zone: | Zone 4b: -25°F to -20°F Zone 4a: -30°F to -25°F | |
| 1990 Hardiness Zone: | Zone 4a: -30F to -25F | |
| Average First Frost Date: | Sep.11 - Sep. 20 | |
| Average Last Frost Date: | Jun. 1 - Jun. 10 | |
| Koppen-Geiger Climate Zone: | Dfb - Humid Continental Mild Summer, Wet All Year | |
| Ecoregion: | 17w - Townsend Basin | |
| Current Drought Status: | Exceptional Drought | |
| Heat Zone Days: | Rare Over 86°F |
Annual Climate Data for ZIP Code 59601 - Helena, MT | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | Annual |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Avg Min Temp (°F) | 11 | 16 | 23 | 31 | 39 | 47 | 52 | 50 | 41 | 31 | 21 | 12 | 31 |
| Avg Max Temp (°F) | 31 | 37 | 46 | 56 | 65 | 75 | 83 | 82 | 70 | 58 | 41 | 32 | 56 |
| Avg Precip (In.) | .48 | .34 | .65 | .94 | 1.8 | 1.77 | 1.31 | 1.34 | 1.06 | .65 | .44 | .45 | 11.23 |