Winchester, New Hampshire has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 2 °C (low) to 14.4 °C (high). Annual precipitation averages 1197.9 Millimeters. Winchester is located in USDA Plant Hardiness Zone 5b. 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 | -11.2 °C | -0.1 °C | 88.39 mm |
| February | -10.4 °C | 1.7 °C | 77.22 mm |
| March | -5.6 °C | 6.3 °C | 90.42 mm |
| April | 0.5 °C | 13.8 °C | 91.69 mm |
| May | 6.7 °C | 20.4 °C | 94.74 mm |
| June | 11.9 °C | 25.2 °C | 112.27 mm |
| July | 14.8 °C | 28.1 °C | 108.46 mm |
| August | 13.8 °C | 27.2 °C | 108.2 mm |
| September | 9.4 °C | 23.1 °C | 104.65 mm |
| October | 3.1 °C | 15.8 °C | 125.22 mm |
| November | -2.1 °C | 8.9 °C | 91.69 mm |
| December | -7.2 °C | 2.8 °C | 104.9 mm |
| Annual | 2 °C | 14.4 °C | 1197.85 mm |
| Average First Frost Date | Oct. 1 - Oct. 10 |
| Average Last Frost Date | May 11 - May 20 |
| 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 | Abnormally Dry |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |