Chinook, Montana has a Cold Semi-Arid Climate climate (Köppen classification: BSk). Average annual temperatures range from -1.3 °C (low) to 13.7 °C (high). Annual precipitation averages 348 Millimeters. 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 | -14.7 °C | -2.2 °C | 10.92 mm |
| February | -13.3 °C | 0.1 °C | 9.91 mm |
| March | -7.4 °C | 6.6 °C | 14.22 mm |
| April | -1.2 °C | 14.1 °C | 27.18 mm |
| May | 4.4 °C | 19.6 °C | 57.4 mm |
| June | 9.5 °C | 24.4 °C | 75.18 mm |
| July | 12.3 °C | 29.5 °C | 43.94 mm |
| August | 11.1 °C | 29.3 °C | 32.77 mm |
| September | 5.5 °C | 23.1 °C | 27.94 mm |
| October | -1.1 °C | 14.3 °C | 20.83 mm |
| November | -7.7 °C | 5.8 °C | 17.53 mm |
| December | -13.1 °C | -0.1 °C | 10.16 mm |
| Annual | -1.3 °C | 13.7 °C | 347.98 mm |
| 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 : -37.2°C to -34.4°C |
| Plant Hardiness Zone - 2012 | Zone 3b : -37.2°C to -34.4°C |
| Current Drought Conditions | Moderate Drought |
| Köppen Climate Classification | BSk - Cold Semi-Arid Climate |