Chinook, Montana has a Cold Semi-Arid Climate climate (Köppen classification: BSk). Average annual temperatures range from 29.7 °F (low) to 56.6 °F (high). Annual precipitation averages 13.7 Inches. Chinook is located in USDA Plant Hardiness Zone 3b. The growing season typically runs from the last frost around May 11 - May 20 through the first frost around Sep. 21 - Sep. 30.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 5.5 °F | 28.0 °F | 0.43 in. |
| February | 8.1 °F | 32.2 °F | 0.39 in. |
| March | 18.7 °F | 43.8 °F | 0.56 in. |
| April | 29.9 °F | 57.3 °F | 1.07 in. |
| May | 39.9 °F | 67.2 °F | 2.26 in. |
| June | 49.1 °F | 75.9 °F | 2.96 in. |
| July | 54.1 °F | 85.1 °F | 1.73 in. |
| August | 52.0 °F | 84.7 °F | 1.29 in. |
| September | 41.9 °F | 73.5 °F | 1.1 in. |
| October | 30.0 °F | 57.7 °F | 0.82 in. |
| November | 18.2 °F | 42.5 °F | 0.69 in. |
| December | 8.5 °F | 31.8 °F | 0.4 in. |
| Annual | 29.7 °F | 56.6 °F | 13.7 in. |
| Average First Frost Date | Sep. 21 - Sep. 30 |
| Average Last Frost Date | May 11 - May 20 |
| Average Days With Frost | Over 180 Days |
| Plant Hardiness Zone | Zone 3b : -35°F to -30°F |
| Plant Hardiness Zone - 2012 | Zone 3b : -35°F to -30°F |
| Current Drought Conditions | Severe Drought |
| Köppen Climate Classification | BSk - Cold Semi-Arid Climate |