Hanover, 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 13.6 °C (high). Annual precipitation averages 1002.3 Millimeters. Hanover is located in USDA Plant Hardiness Zone 5a. The growing season typically runs from the last frost around May 1 - May 10 through the first frost around Oct. 11 - Oct. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -13 °C | -1.7 °C | 68.83 mm |
| February | -12.2 °C | 0.3 °C | 61.21 mm |
| March | -7.1 °C | 5.2 °C | 77.98 mm |
| April | -0.3 °C | 13.2 °C | 81.28 mm |
| May | 6.3 °C | 20.3 °C | 80.01 mm |
| June | 11.3 °C | 24.9 °C | 90.68 mm |
| July | 14.4 °C | 27.7 °C | 107.7 mm |
| August | 13.4 °C | 26.8 °C | 84.33 mm |
| September | 9.2 °C | 22.7 °C | 87.63 mm |
| October | 2.8 °C | 14.9 °C | 101.85 mm |
| November | -2.5 °C | 7.9 °C | 76.45 mm |
| December | -8.1 °C | 1.2 °C | 84.33 mm |
| Annual | 1.2 °C | 13.6 °C | 1002.28 mm |
| Average First Frost Date | Oct. 11 - Oct. 20 |
| Average Last Frost Date | May 1 - May 10 |
| Average Days With Frost | 125-150 Days |
| Plant Hardiness Zone | Zone 5a : -28.9°C to -26.1°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 |