| 2023 Hardiness Zone: | Zone 5a: -20°F to -15°F Zone 4b: -25°F to -20°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. 21 - Sep. 30 |
| Average Last Frost Date: | Jun. 1 - Jun. 10 |
| Koppen-Geiger Climate Zone: | BSk - Cold Semi-Arid Climate |
| Ecoregion: | 43p - Ponderosa Pine Forest-Savanna Hills |
| Heat Zone Days: | 46 - 60 days Over 86°F |
Annual Climate Data for ZIP Code 59072 - Roundup, MT | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | Annual |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Avg Min Temp (°F) | 12 | 17 | 24 | 32 | 41 | 49 | 54 | 53 | 43 | 34 | 22 | 15 | 33 |
| Avg Max Temp (°F) | 36 | 42 | 50 | 59 | 69 | 78 | 86 | 85 | 74 | 62 | 45 | 38 | 60 |
| Avg Precip (In.) | .45 | .36 | .66 | 1.3 | 2.39 | 2.16 | 1.66 | 1.28 | 1.28 | 1.03 | .36 | .47 | 13.39 |