Henniker, New Hampshire has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 1.7 °C (low) to 14 °C (high). Annual precipitation averages 1221.5 Millimeters. Henniker 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 | -11.5 °C | -0.5 °C | 83.57 mm |
| February | -10.7 °C | 1.2 °C | 82.04 mm |
| March | -5.9 °C | 5.8 °C | 94.23 mm |
| April | 0.1 °C | 13.2 °C | 98.81 mm |
| May | 6.4 °C | 19.7 °C | 95 mm |
| June | 11.7 °C | 24.7 °C | 113.79 mm |
| July | 14.7 °C | 27.7 °C | 105.16 mm |
| August | 13.5 °C | 26.8 °C | 99.06 mm |
| September | 9.3 °C | 22.6 °C | 103.12 mm |
| October | 2.8 °C | 15.2 °C | 130.05 mm |
| November | -2.2 °C | 8.6 °C | 101.6 mm |
| December | -7.4 °C | 2.6 °C | 115.06 mm |
| Annual | 1.7 °C | 14 °C | 1221.49 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 | Abnormally Dry |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |