Winnett, Montana has a Cold Semi-Arid Climate climate (Köppen classification: BSk). Average annual temperatures range from 0.4 °C (low) to 15.3 °C (high). Annual precipitation averages 350.5 Millimeters. Winnett is located in USDA Plant Hardiness Zone 4b. 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 | -11.4 °C | 1.4 °C | 11.68 mm |
| February | -9.9 °C | 3.2 °C | 9.91 mm |
| March | -5.2 °C | 8.8 °C | 14.99 mm |
| April | -0.3 °C | 14.6 °C | 35.31 mm |
| May | 4.9 °C | 19.7 °C | 66.29 mm |
| June | 9.7 °C | 24.6 °C | 64.77 mm |
| July | 13.2 °C | 30.6 °C | 37.34 mm |
| August | 12.1 °C | 30.3 °C | 33.27 mm |
| September | 6.7 °C | 24.2 °C | 26.16 mm |
| October | 0.6 °C | 15.9 °C | 28.7 mm |
| November | -5.6 °C | 8 °C | 10.67 mm |
| December | -10.5 °C | 2.3 °C | 11.43 mm |
| Annual | 0.4 °C | 15.3 °C | 350.52 mm |
| Average First Frost Date | Sep. 21 - Sep. 30 |
| Average Last Frost Date | May 11 - May 20 |
| Average Days With Frost | 150-180 Days |
| Plant Hardiness Zone | Zone 4b : -31.7°C to -28.9°C |
| Plant Hardiness Zone - 2012 | Zone 4a : -34.4°C to -31.7°C |
| Current Drought Conditions | Moderate Drought |
| Köppen Climate Classification | BSk - Cold Semi-Arid Climate |