Plainfield, New Hampshire has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 34.2 °F (low) to 56.1 °F (high). Annual precipitation averages 41.3 Inches. 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 | 8.8 °F | 29.0 °F | 2.79 in. |
| February | 10.1 °F | 32.6 °F | 2.45 in. |
| March | 19.5 °F | 41.1 °F | 2.95 in. |
| April | 31.7 °F | 55.1 °F | 3.35 in. |
| May | 43.4 °F | 67.7 °F | 3.39 in. |
| June | 52.6 °F | 75.9 °F | 4.13 in. |
| July | 57.8 °F | 81.2 °F | 4.29 in. |
| August | 56.0 °F | 79.5 °F | 3.44 in. |
| September | 48.6 °F | 72.5 °F | 3.38 in. |
| October | 37.0 °F | 58.3 °F | 4.52 in. |
| November | 27.5 °F | 46.1 °F | 3.11 in. |
| December | 17.5 °F | 34.4 °F | 3.54 in. |
| Annual | 34.2 °F | 56.1 °F | 41.34 in. |
| 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 : -20°F to -15°F |
| Plant Hardiness Zone - 2012 | Zone 5a : -20°F to -15°F |
| Current Drought Conditions | Abnormally Dry |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |