Westhampton, Massachusetts has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 2.2 °C (low) to 14.3 °C (high). Annual precipitation averages 1296.7 Millimeters. Westhampton is located in USDA Plant Hardiness Zone 6a. The growing season typically runs from the last frost around May 11 - May 20 through the first frost around Oct. 1 - Oct. 10.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -10.6 °C | 0.1 °C | 90.42 mm |
| February | -9.9 °C | 1.6 °C | 84.07 mm |
| March | -5.3 °C | 6.2 °C | 102.87 mm |
| April | 0.8 °C | 13.7 °C | 105.66 mm |
| May | 6.8 °C | 20.2 °C | 103.63 mm |
| June | 12 °C | 24.7 °C | 118.11 mm |
| July | 14.9 °C | 27.6 °C | 109.22 mm |
| August | 13.8 °C | 26.6 °C | 111.76 mm |
| September | 9.6 °C | 22.7 °C | 122.68 mm |
| October | 3.4 °C | 15.8 °C | 133.1 mm |
| November | -1.9 °C | 9 °C | 99.82 mm |
| December | -6.8 °C | 2.9 °C | 115.32 mm |
| Annual | 2.2 °C | 14.3 °C | 1296.66 mm |
| Average First Frost Date | Oct. 1 - Oct. 10 |
| Average Last Frost Date | May 11 - May 20 |
| Average Days With Frost | 125-150 Days |
| Plant Hardiness Zone | Zone 6a : -23.3°C to -20.6°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 |