Dillon, Montana has a Cold Semi-Arid Climate climate (Köppen classification: BSk). Average annual temperatures range from -1 °C (low) to 13.8 °C (high). Annual precipitation averages 282.7 Millimeters. Dillon is located in USDA Plant Hardiness Zone 5a. The growing season typically runs from the last frost around Jun. 1 - Jun. 10 through the first frost around Sep.11 - Sep. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -9.7 °C | 1.2 °C | 7.62 mm |
| February | -9 °C | 3.1 °C | 8.89 mm |
| March | -5.2 °C | 7.9 °C | 14.99 mm |
| April | -1.7 °C | 12.7 °C | 35.31 mm |
| May | 2.6 °C | 18 °C | 48.01 mm |
| June | 6.2 °C | 22.7 °C | 48.51 mm |
| July | 9.1 °C | 28.8 °C | 23.88 mm |
| August | 8 °C | 28 °C | 22.86 mm |
| September | 4.3 °C | 22.3 °C | 22.35 mm |
| October | -0.9 °C | 14.4 °C | 25.65 mm |
| November | -5.9 °C | 6.3 °C | 12.95 mm |
| December | -10.3 °C | 0.6 °C | 11.68 mm |
| Annual | -1 °C | 13.8 °C | 282.7 mm |
| Average First Frost Date | Sep.11 - Sep. 20 |
| Average Last Frost Date | Jun. 1 - Jun. 10 |
| Average Days With Frost | Over 180 Days |
| Plant Hardiness Zone | Zone 5a : -28.9°C to -26.1°C |
| Plant Hardiness Zone - 2012 | Zone 4b : -31.7°C to -28.9°C |
| Current Drought Conditions | Severe Drought |
| Köppen Climate Classification | BSk - Cold Semi-Arid Climate |