Westmoreland, 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 13.9 °C (high). Annual precipitation averages 1167.4 Millimeters. Westmoreland is located in USDA Plant Hardiness Zone 5b. The growing season typically runs from the last frost around May 21 - May 31 through the first frost around Sep. 21 - Sep. 30.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -11.6 °C | -0.7 °C | 83.31 mm |
| February | -10.7 °C | 1.2 °C | 71.63 mm |
| March | -6 °C | 5.7 °C | 84.07 mm |
| April | 0.3 °C | 13.3 °C | 87.38 mm |
| May | 6.4 °C | 19.9 °C | 96.01 mm |
| June | 11.6 °C | 24.7 °C | 109.98 mm |
| July | 14.6 °C | 27.6 °C | 110.24 mm |
| August | 13.3 °C | 26.7 °C | 108.46 mm |
| September | 9 °C | 22.7 °C | 102.62 mm |
| October | 2.8 °C | 15.5 °C | 122.94 mm |
| November | -2.3 °C | 8.5 °C | 88.65 mm |
| December | -7.4 °C | 2.2 °C | 102.11 mm |
| Annual | 1.7 °C | 13.9 °C | 1167.4 mm |
| Average First Frost Date | Sep. 21 - Sep. 30 |
| Average Last Frost Date | May 21 - May 31 |
| 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 | Normal |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |