Williston, Vermont has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 1.3 °C (low) to 12.3 °C (high). Annual precipitation averages 1092.4 Millimeters. Williston is located in USDA Plant Hardiness Zone 5a. 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 | -13.1 °C | -2.6 °C | 64.26 mm |
| February | -12.5 °C | -1.1 °C | 53.09 mm |
| March | -7.3 °C | 3.7 °C | 70.1 mm |
| April | 0 °C | 11.3 °C | 89.66 mm |
| May | 6.6 °C | 18.9 °C | 99.31 mm |
| June | 11.8 °C | 23.7 °C | 117.09 mm |
| July | 14.7 °C | 26.2 °C | 120.9 mm |
| August | 13.7 °C | 25.2 °C | 108.71 mm |
| September | 9.3 °C | 21.1 °C | 101.6 mm |
| October | 3.2 °C | 13.6 °C | 109.22 mm |
| November | -2.2 °C | 7.1 °C | 80.01 mm |
| December | -8.3 °C | 0.7 °C | 78.49 mm |
| Annual | 1.3 °C | 12.3 °C | 1092.44 mm |
| 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 5a : -28.9°C to -26.1°C |
| Plant Hardiness Zone - 2012 | Zone 4b : -31.7°C to -28.9°C |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |