Harrisville, New Hampshire has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 3.3 °C (low) to 12.9 °C (high). Annual precipitation averages 1327.7 Millimeters. Harrisville 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 | -9.9 °C | -1.5 °C | 97.79 mm |
| February | -8.6 °C | 0.4 °C | 92.96 mm |
| March | -4.9 °C | 4.5 °C | 107.44 mm |
| April | 1.7 °C | 12.7 °C | 97.79 mm |
| May | 6.8 °C | 18.9 °C | 101.6 mm |
| June | 13.5 °C | 23.6 °C | 116.08 mm |
| July | 16.7 °C | 26.2 °C | 126.49 mm |
| August | 13.9 °C | 25.3 °C | 113.79 mm |
| September | 9.6 °C | 21.2 °C | 108.71 mm |
| October | 5.8 °C | 14.2 °C | 139.7 mm |
| November | -0.4 °C | 7.6 °C | 105.16 mm |
| December | -5 °C | 1.7 °C | 120.14 mm |
| Annual | 3.3 °C | 12.9 °C | 1327.65 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 6a : -23.3°C to -20.6°C |
| Current Drought Conditions | Abnormally Dry |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |