Greenfield, New Hampshire has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 1.9 °C (low) to 13.7 °C (high). Annual precipitation averages 1242.6 Millimeters. Greenfield 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 | -10.9 °C | -0.6 °C | 89.92 mm |
| February | -10.2 °C | 1.2 °C | 83.31 mm |
| March | -5.8 °C | 5.6 °C | 102.62 mm |
| April | 0.3 °C | 13.2 °C | 99.57 mm |
| May | 6.3 °C | 19.3 °C | 98.04 mm |
| June | 11.6 °C | 24.2 °C | 111.76 mm |
| July | 14.5 °C | 27 °C | 104.9 mm |
| August | 13.4 °C | 26.1 °C | 103.38 mm |
| September | 9.2 °C | 22.1 °C | 106.43 mm |
| October | 3.2 °C | 14.9 °C | 132.33 mm |
| November | -1.9 °C | 8.5 °C | 98.81 mm |
| December | -7.2 °C | 2.6 °C | 111.51 mm |
| Annual | 1.9 °C | 13.7 °C | 1242.58 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 5b : -26.1°C to -23.3°C |
| Current Drought Conditions | Moderate Drought |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |