Colebrook, Connecticut has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 2.9 °C (low) to 13.8 °C (high). Annual precipitation averages 1335.8 Millimeters. Colebrook 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. 1 - Oct. 10.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -9.4 °C | 0.1 °C | 93.73 mm |
| February | -8.7 °C | 1.6 °C | 83.57 mm |
| March | -4.5 °C | 6.1 °C | 107.7 mm |
| April | 1.3 °C | 13.5 °C | 102.11 mm |
| May | 7.2 °C | 19.7 °C | 107.7 mm |
| June | 12.2 °C | 24.1 °C | 123.44 mm |
| July | 14.9 °C | 26.7 °C | 118.62 mm |
| August | 13.8 °C | 25.8 °C | 116.33 mm |
| September | 9.9 °C | 21.8 °C | 125.48 mm |
| October | 4.4 °C | 15.2 °C | 138.18 mm |
| November | -0.9 °C | 8.4 °C | 101.6 mm |
| December | -5.8 °C | 3 °C | 117.35 mm |
| Annual | 2.9 °C | 13.8 °C | 1335.81 mm |
| Average First Frost Date | Oct. 1 - Oct. 10 |
| Average Last Frost Date | May 1 - May 10 |
| Average Days With Frost | 125-150 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 | Dfb - Humid Continental Mild Summer, Wet All Year |