Windham, New Hampshire has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 37.4 °F (low) to 59 °F (high). Annual precipitation averages 47.6 Inches. Windham is located in USDA Plant Hardiness Zone 6a. 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 | 14.5 °F | 33.9 °F | 3.28 in. |
| February | 16.3 °F | 36.8 °F | 3.28 in. |
| March | 24.1 °F | 44.6 °F | 4.15 in. |
| April | 34.8 °F | 57.7 °F | 4.02 in. |
| May | 45.3 °F | 68.5 °F | 3.85 in. |
| June | 54.7 °F | 77.4 °F | 4.33 in. |
| July | 60.4 °F | 82.8 °F | 3.77 in. |
| August | 58.6 °F | 81.4 °F | 3.8 in. |
| September | 50.9 °F | 74.2 °F | 4.05 in. |
| October | 38.9 °F | 61.5 °F | 4.85 in. |
| November | 29.8 °F | 50.1 °F | 3.9 in. |
| December | 21.0 °F | 39.4 °F | 4.35 in. |
| Annual | 37.4 °F | 59 °F | 47.63 in. |
| Average First Frost Date | Oct. 1 - Oct. 10 |
| Average Last Frost Date | May 1 - May 10 |
| Average Days With Frost | 125-150 Days |
| Plant Hardiness Zone | Zone 6a : -10°F to -5°F |
| Plant Hardiness Zone - 2012 | Zone 5b : -15°F to -10°F |
| Current Drought Conditions | Severe Drought |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |