New London, New Hampshire has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 2.2 °C (low) to 12.7 °C (high). Annual precipitation averages 1243.6 Millimeters. New London is located in USDA Plant Hardiness Zone 6a. The growing season typically runs from the last frost around May 21 - May 31 through the first frost around Sep. 21 - Sep. 30.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -10.8 °C | -1.8 °C | 84.84 mm |
| February | -9.9 °C | -0.1 °C | 77.72 mm |
| March | -5.7 °C | 4.5 °C | 92.46 mm |
| April | 0.3 °C | 11.9 °C | 99.82 mm |
| May | 6.7 °C | 18.9 °C | 100.58 mm |
| June | 12 °C | 23.5 °C | 117.35 mm |
| July | 14.8 °C | 26 °C | 116.08 mm |
| August | 14.1 °C | 25.3 °C | 105.16 mm |
| September | 10 °C | 21.3 °C | 101.09 mm |
| October | 3.7 °C | 13.8 °C | 135.64 mm |
| November | -1.4 °C | 7.6 °C | 101.6 mm |
| December | -7.1 °C | 1.1 °C | 111.25 mm |
| Annual | 2.2 °C | 12.7 °C | 1243.59 mm |
| Average First Frost Date | Sep. 21 - Sep. 30 |
| Average Last Frost Date | May 21 - May 31 |
| Average Days With Frost | 150-180 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 | Normal |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |