Dillon, Colorado has a Subarctic With Cool Summers And Year Around Rainfall climate (Köppen classification: Dfc). Average annual temperatures range from -5.4 °C (low) to 11.1 °C (high). Annual precipitation averages 396.8 Millimeters. Dillon is located in USDA Plant Hardiness Zone 5a. The growing season typically runs from the last frost around Jun. 21 - Jun. 30 through the first frost around July 21 - July 31.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -14.6 °C | -0.1 °C | 27.18 mm |
| February | -13.9 °C | 1.2 °C | 27.69 mm |
| March | -10.3 °C | 5.3 °C | 31.5 mm |
| April | -6.4 °C | 8.9 °C | 39.88 mm |
| May | -2 °C | 14.4 °C | 35.56 mm |
| June | 1.7 °C | 20.8 °C | 28.19 mm |
| July | 4.9 °C | 23.8 °C | 46.99 mm |
| August | 4.2 °C | 22.5 °C | 48.01 mm |
| September | 0.4 °C | 18.9 °C | 36.32 mm |
| October | -4.5 °C | 12.1 °C | 26.16 mm |
| November | -10 °C | 4.9 °C | 24.38 mm |
| December | -14.5 °C | -0.1 °C | 24.89 mm |
| Annual | -5.4 °C | 11.1 °C | 396.75 mm |
| Average First Frost Date | July 21 - July 31 |
| Average Last Frost Date | Jun. 21 - Jun. 30 |
| 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 | Exceptional Drought |
| Köppen Climate Classification | Dfc - Subarctic With Cool Summers And Year Around Rainfall |