Andover, New Hampshire has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 1.2 °C (low) to 13.5 °C (high). Annual precipitation averages 1210.1 Millimeters. Andover is located in USDA Plant Hardiness Zone 5b. 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 | -12.1 °C | -1.3 °C | 81.53 mm |
| February | -11.5 °C | 0.4 °C | 75.69 mm |
| March | -6.6 °C | 5.2 °C | 87.63 mm |
| April | -0.3 °C | 12.8 °C | 97.54 mm |
| May | 5.9 °C | 19.7 °C | 98.55 mm |
| June | 11.1 °C | 24.5 °C | 113.54 mm |
| July | 14.2 °C | 27.4 °C | 112.01 mm |
| August | 13 °C | 26.5 °C | 101.35 mm |
| September | 8.8 °C | 22.3 °C | 98.55 mm |
| October | 2.4 °C | 14.8 °C | 135.64 mm |
| November | -2.5 °C | 7.9 °C | 99.31 mm |
| December | -7.8 °C | 1.8 °C | 108.71 mm |
| Annual | 1.2 °C | 13.5 °C | 1210.05 mm |
| Average First Frost Date | Oct. 1 - Oct. 10 |
| Average Last Frost Date | May 1 - May 10 |
| Average Days With Frost | 150-180 Days |
| Plant Hardiness Zone | Zone 5b : -26.1°C to -23.3°C |
| Plant Hardiness Zone - 2012 | Zone 5a : -28.9°C to -26.1°C |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |