Somersworth, New Hampshire has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 3 °C (low) to 14.1 °C (high). Annual precipitation averages 1174.8 Millimeters. Somersworth is located in USDA Plant Hardiness Zone 6a. 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 | -9.8 °C | 0.3 °C | 83.57 mm |
| February | -8.9 °C | 1.8 °C | 82.55 mm |
| March | -4.3 °C | 6 °C | 104.65 mm |
| April | 1.4 °C | 13.1 °C | 108.2 mm |
| May | 7.1 °C | 19.1 °C | 91.44 mm |
| June | 12.3 °C | 24.3 °C | 103.38 mm |
| July | 15.4 °C | 27.4 °C | 93.22 mm |
| August | 14.6 °C | 26.8 °C | 87.63 mm |
| September | 10.3 °C | 22.7 °C | 90.68 mm |
| October | 4.2 °C | 15.7 °C | 120.9 mm |
| November | -0.9 °C | 9.3 °C | 97.79 mm |
| December | -6 °C | 3.2 °C | 110.74 mm |
| Annual | 3 °C | 14.1 °C | 1174.75 mm |
| Average First Frost Date | Oct. 1 - Oct. 10 |
| Average Last Frost Date | May 1 - May 10 |
| Average Days With Frost | 125-150 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 | Moderate Drought |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |