Plainfield, 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 13.4 °C (high). Annual precipitation averages 1050.1 Millimeters. Plainfield 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. 1 - Oct. 10.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -12.9 °C | -1.7 °C | 70.87 mm |
| February | -12.2 °C | 0.3 °C | 62.23 mm |
| March | -6.9 °C | 5.1 °C | 74.93 mm |
| April | -0.2 °C | 12.8 °C | 85.09 mm |
| May | 6.3 °C | 19.8 °C | 86.11 mm |
| June | 11.4 °C | 24.4 °C | 104.9 mm |
| July | 14.3 °C | 27.3 °C | 108.97 mm |
| August | 13.3 °C | 26.4 °C | 87.38 mm |
| September | 9.2 °C | 22.5 °C | 85.85 mm |
| October | 2.8 °C | 14.6 °C | 114.81 mm |
| November | -2.5 °C | 7.8 °C | 78.99 mm |
| December | -8.1 °C | 1.3 °C | 89.92 mm |
| Annual | 1.2 °C | 13.4 °C | 1050.05 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 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 |