Hartsel, Colorado has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from -6 °C (low) to 12.4 °C (high). Annual precipitation averages 293.9 Millimeters. Hartsel is located in USDA Plant Hardiness Zone 4a. The growing season typically runs from the last frost around Jun. 21 - Jun. 30 through the first frost around Aug. 11 - Aug. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -16.3 °C | 1.6 °C | 10.67 mm |
| February | -15.1 °C | 2.5 °C | 7.37 mm |
| March | -10.3 °C | 6.6 °C | 19.81 mm |
| April | -6.5 °C | 10.1 °C | 24.64 mm |
| May | -2.1 °C | 15.7 °C | 26.92 mm |
| June | 1.9 °C | 22.1 °C | 21.84 mm |
| July | 5.2 °C | 24.9 °C | 52.58 mm |
| August | 4.4 °C | 23.4 °C | 56.64 mm |
| September | 0.1 °C | 20 °C | 31.75 mm |
| October | -5.9 °C | 13.6 °C | 19.56 mm |
| November | -11 °C | 6.9 °C | 9.65 mm |
| December | -16.4 °C | 1.5 °C | 12.45 mm |
| Annual | -6 °C | 12.4 °C | 293.88 mm |
| Average First Frost Date | Aug. 11 - Aug. 20 |
| Average Last Frost Date | Jun. 21 - Jun. 30 |
| Average Days With Frost | Over 180 Days |
| Plant Hardiness Zone | Zone 4a : -34.4°C to -31.7°C |
| Plant Hardiness Zone - 2012 | Zone 3b : -37.2°C to -34.4°C |
| Current Drought Conditions | Extreme Drought |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |