Dillon, Montana has a Cold Semi-Arid Climate climate (Köppen classification: BSk). Average annual temperatures range from 30.1 °F (low) to 56.9 °F (high). Annual precipitation averages 11.1 Inches. 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 | 14.5 °F | 34.1 °F | 0.3 in. |
| February | 15.8 °F | 37.5 °F | 0.35 in. |
| March | 22.6 °F | 46.3 °F | 0.59 in. |
| April | 28.9 °F | 54.9 °F | 1.39 in. |
| May | 36.7 °F | 64.4 °F | 1.89 in. |
| June | 43.2 °F | 72.9 °F | 1.91 in. |
| July | 48.4 °F | 83.8 °F | 0.94 in. |
| August | 46.4 °F | 82.4 °F | 0.9 in. |
| September | 39.7 °F | 72.1 °F | 0.88 in. |
| October | 30.4 °F | 58.0 °F | 1.01 in. |
| November | 21.4 °F | 43.4 °F | 0.51 in. |
| December | 13.4 °F | 33.1 °F | 0.46 in. |
| Annual | 30.1 °F | 56.9 °F | 11.13 in. |
| 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 : -20°F to -15°F |
| Plant Hardiness Zone - 2012 | Zone 4b : -25°F to -20°F |
| Current Drought Conditions | Extreme Drought |
| Köppen Climate Classification | BSk - Cold Semi-Arid Climate |