| 2023 Hardiness Zone: | Zone 3b: -35°F to -30°F Zone 4a: -30°F to -25°F | |
| 2012 Hardiness Zone: | Zone 3b: -35°F to -30°F Zone 4a: -30°F to -25°F | |
| 1990 Hardiness Zone: | Zone 3a: -40F to -35F | |
| 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: | 42j - Glaciated Northern Grasslands | |
| Current Drought Status: | Exceptional Drought | |
| Heat Zone Days: | 15 - 30 days Over 86°F |
Annual Climate Data for ZIP Code 59526 - Harlem, MT | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | Annual |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Avg Min Temp (°F) | 1 | 8 | 19 | 29 | 40 | 48 | 52 | 50 | 39 | 29 | 15 | 5 | 28 |
| Avg Max Temp (°F) | 26 | 34 | 46 | 60 | 70 | 79 | 85 | 85 | 73 | 61 | 41 | 30 | 58 |
| Avg Precip (In.) | .42 | .32 | .39 | .75 | 1.98 | 2.2 | 1.81 | 1.03 | 1.33 | .56 | .4 | .42 | 11.62 |