Bolton, Connecticut has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 4 °C (low) to 14.6 °C (high). Annual precipitation averages 1190.8 Millimeters. Bolton is located in USDA Plant Hardiness Zone 6b. 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 | -7.8 °C | 1.4 °C | 85.34 mm |
| February | -7.3 °C | 2.9 °C | 74.17 mm |
| March | -3.3 °C | 7.1 °C | 107.19 mm |
| April | 2.3 °C | 13.6 °C | 98.55 mm |
| May | 7.7 °C | 19.4 °C | 92.46 mm |
| June | 12.9 °C | 24.1 °C | 103.89 mm |
| July | 16 °C | 27 °C | 104.39 mm |
| August | 15.2 °C | 26.2 °C | 103.38 mm |
| September | 11.3 °C | 22.4 °C | 108.46 mm |
| October | 5.2 °C | 15.9 °C | 114.05 mm |
| November | 0.2 °C | 10.2 °C | 92.46 mm |
| December | -4.1 °C | 4.7 °C | 106.43 mm |
| Annual | 4 °C | 14.6 °C | 1190.77 mm |
| Average First Frost Date | Oct. 11 - Oct. 20 |
| Average Last Frost Date | Apr. 21 - Apr. 30 |
| Average Days With Frost | 125-150 Days |
| Plant Hardiness Zone | Zone 6b : -20.6°C to -17.8°C |
| Plant Hardiness Zone - 2012 | Zone 6a : -23.3°C to -20.6°C |
| Current Drought Conditions | Moderate Drought |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |