Grafton, Vermont has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 33.2 °F (low) to 55.1 °F (high). Annual precipitation averages 48.3 Inches. Grafton 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 Sep. 21 - Sep. 30.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 9.5 °F | 29.1 °F | 3.49 in. |
| February | 10.2 °F | 32.1 °F | 2.89 in. |
| March | 18.6 °F | 40.1 °F | 3.77 in. |
| April | 30.6 °F | 53.4 °F | 3.88 in. |
| May | 42.3 °F | 66.2 °F | 4.04 in. |
| June | 51.4 °F | 74.5 °F | 4.63 in. |
| July | 56.2 °F | 79.5 °F | 4.28 in. |
| August | 54.3 °F | 78.1 °F | 4.07 in. |
| September | 46.3 °F | 71.0 °F | 4.05 in. |
| October | 35.2 °F | 57.5 °F | 5.12 in. |
| November | 26.3 °F | 45.6 °F | 3.82 in. |
| December | 17.3 °F | 34.3 °F | 4.21 in. |
| Annual | 33.2 °F | 55.1 °F | 48.25 in. |
| Average First Frost Date | Sep. 21 - Sep. 30 |
| Average Last Frost Date | May 11 - May 20 |
| Average Days With Frost | 150-180 Days |
| Plant Hardiness Zone | Zone 5b : -15°F to -10°F |
| Plant Hardiness Zone - 2012 | Zone 5a : -20°F to -15°F |
| Current Drought Conditions | Abnormally Dry |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |