Winchendon, Massachusetts has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 1.9 °C (low) to 13.6 °C (high). Annual precipitation averages 1244.1 Millimeters. Winchendon 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 | -11.1 °C | -0.4 °C | 94.23 mm |
| February | -10.3 °C | 1.2 °C | 82.3 mm |
| March | -5.8 °C | 5.6 °C | 101.35 mm |
| April | 0.4 °C | 12.8 °C | 97.79 mm |
| May | 6.5 °C | 19.3 °C | 95 mm |
| June | 11.6 °C | 24.1 °C | 115.57 mm |
| July | 14.7 °C | 26.9 °C | 110.24 mm |
| August | 13.7 °C | 26.1 °C | 108.97 mm |
| September | 9.4 °C | 22 °C | 107.95 mm |
| October | 3.2 °C | 14.7 °C | 128.02 mm |
| November | -1.9 °C | 8.3 °C | 95.5 mm |
| December | -7.2 °C | 2.5 °C | 107.19 mm |
| Annual | 1.9 °C | 13.6 °C | 1244.11 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 5a : -28.9°C to -26.1°C |
| Current Drought Conditions | Moderate Drought |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |