| 2023 Hardiness Zone: | Zone 3b: -35°F to -30°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 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 59523 - Chinook, MT | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | Annual |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Avg Min Temp (°F) | 1 | 7 | 18 | 30 | 41 | 49 | 53 | 51 | 39 | 28 | 14 | 5 | 28 |
| Avg Max Temp (°F) | 26 | 34 | 45 | 59 | 69 | 78 | 84 | 84 | 72 | 60 | 41 | 30 | 57 |
| Avg Precip (In.) | .53 | .31 | .55 | 1 | 2.28 | 2.27 | 1.66 | 1.33 | 1.42 | .66 | .46 | .51 | 12.98 |