Holly, Colorado has a Cold Semi-Arid Climate climate (Köppen classification: BSk). Average annual temperatures range from 3.1 °C (low) to 20.6 °C (high). Annual precipitation averages 450.1 Millimeters. Holly is located in USDA Plant Hardiness Zone 6a. The growing season typically runs from the last frost around Apr. 21 - Apr. 30 through the first frost around Oct. 11 - Oct. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -9.5 °C | 7.6 °C | 8.64 mm |
| February | -7.6 °C | 9.8 °C | 8.64 mm |
| March | -3.1 °C | 15.2 °C | 23.11 mm |
| April | 1.7 °C | 20 °C | 38.1 mm |
| May | 7.9 °C | 25.3 °C | 60.2 mm |
| June | 14.2 °C | 31.3 °C | 68.83 mm |
| July | 17.1 °C | 33.6 °C | 74.42 mm |
| August | 16.2 °C | 32.3 °C | 82.55 mm |
| September | 10.8 °C | 28.7 °C | 28.45 mm |
| October | 2.5 °C | 21.4 °C | 34.54 mm |
| November | -4.2 °C | 13.7 °C | 12.45 mm |
| December | -8.9 °C | 7.8 °C | 10.16 mm |
| Annual | 3.1 °C | 20.6 °C | 450.09 mm |
| Average First Frost Date | Oct. 11 - Oct. 20 |
| Average Last Frost Date | Apr. 21 - Apr. 30 |
| Average Days With Frost | 150-180 Days |
| Plant Hardiness Zone | Zone 6a : -23.3°C to -20.6°C |
| Plant Hardiness Zone - 2012 | Zone 5b : -26.1°C to -23.3°C |
| Current Drought Conditions | Moderate Drought |
| Köppen Climate Classification | BSk - Cold Semi-Arid Climate |