Hartman, Colorado has a Cold Semi-Arid Climate climate (Köppen classification: BSk). Average annual temperatures range from 2.9 °C (low) to 20 °C (high). Annual precipitation averages 439.9 Millimeters. Hartman is located in USDA Plant Hardiness Zone 6a. The growing season typically runs from the last frost around May 1 - May 10 through the first frost around Oct. 11 - Oct. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -9.5 °C | 7.2 °C | 8.38 mm |
| February | -7.7 °C | 9.3 °C | 9.14 mm |
| March | -3.4 °C | 14.9 °C | 22.35 mm |
| April | 1.4 °C | 19.3 °C | 37.59 mm |
| May | 7.7 °C | 24.6 °C | 57.91 mm |
| June | 13.9 °C | 30.7 °C | 66.55 mm |
| July | 16.8 °C | 33.1 °C | 74.42 mm |
| August | 15.8 °C | 31.7 °C | 78.74 mm |
| September | 10.8 °C | 27.9 °C | 28.19 mm |
| October | 2.6 °C | 20.9 °C | 34.04 mm |
| November | -4.2 °C | 13.3 °C | 12.19 mm |
| December | -9 °C | 7.5 °C | 10.41 mm |
| Annual | 2.9 °C | 20 °C | 439.91 mm |
| Average First Frost Date | Oct. 11 - Oct. 20 |
| Average Last Frost Date | May 1 - May 10 |
| Average Days With Frost | 150-180 Days |
| Plant Hardiness Zone | Zone 6a : -23.3°C to -20.6°C |
| Plant Hardiness Zone - 2012 | Zone 6a : -23.3°C to -20.6°C |
| Current Drought Conditions | Severe Drought |
| Köppen Climate Classification | BSk - Cold Semi-Arid Climate |