Williamsburg, Massachusetts has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 2 °C (low) to 14.1 °C (high). Annual precipitation averages 1306.6 Millimeters. Williamsburg 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 | -11.1 °C | -0.2 °C | 91.44 mm |
| February | -10.3 °C | 1.5 °C | 84.84 mm |
| March | -5.6 °C | 6.1 °C | 104.39 mm |
| April | 0.6 °C | 13.4 °C | 106.68 mm |
| May | 6.7 °C | 19.9 °C | 102.62 mm |
| June | 11.8 °C | 24.6 °C | 121.16 mm |
| July | 14.7 °C | 27.4 °C | 111 mm |
| August | 13.6 °C | 26.4 °C | 112.27 mm |
| September | 9.3 °C | 22.5 °C | 123.7 mm |
| October | 3.2 °C | 15.4 °C | 133.1 mm |
| November | -2.3 °C | 8.8 °C | 101.09 mm |
| December | -7.2 °C | 2.8 °C | 114.3 mm |
| Annual | 2 °C | 14.1 °C | 1306.59 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 |