Andover, Connecticut has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 4.1 °C (low) to 15.4 °C (high). Annual precipitation averages 1251.5 Millimeters. Andover 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 | -8 °C | 2.2 °C | 90.93 mm |
| February | -7.2 °C | 3.6 °C | 78.74 mm |
| March | -3 °C | 7.9 °C | 110.49 mm |
| April | 2.6 °C | 14.6 °C | 108.97 mm |
| May | 8 °C | 20.4 °C | 92.2 mm |
| June | 13.2 °C | 25.1 °C | 109.47 mm |
| July | 16.4 °C | 27.9 °C | 102.11 mm |
| August | 15.4 °C | 27.1 °C | 111 mm |
| September | 11.2 °C | 23.3 °C | 114.3 mm |
| October | 4.9 °C | 16.8 °C | 122.94 mm |
| November | -0.2 °C | 10.8 °C | 98.3 mm |
| December | -4.6 °C | 5.3 °C | 112.01 mm |
| Annual | 4.1 °C | 15.4 °C | 1251.46 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 |