Grafton, Massachusetts has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 38.8 °F (low) to 59.1 °F (high). Annual precipitation averages 49.3 Inches. Grafton is located in USDA Plant Hardiness Zone 6b. The growing season typically runs from the last frost around Apr. 11 - Apr. 20 through the first frost around Oct. 21 - Oct. 31.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 16.3 °F | 34.8 °F | 3.83 in. |
| February | 17.7 °F | 37.5 °F | 3.4 in. |
| March | 25.5 °F | 45.1 °F | 4.62 in. |
| April | 35.9 °F | 57.7 °F | 4.4 in. |
| May | 46.5 °F | 68.3 °F | 3.53 in. |
| June | 55.8 °F | 76.5 °F | 4.2 in. |
| July | 61.6 °F | 81.9 °F | 3.78 in. |
| August | 60.0 °F | 80.5 °F | 4.09 in. |
| September | 52.1 °F | 73.8 °F | 3.95 in. |
| October | 40.8 °F | 61.8 °F | 4.92 in. |
| November | 31.2 °F | 50.7 °F | 3.86 in. |
| December | 22.7 °F | 40.4 °F | 4.75 in. |
| Annual | 38.8 °F | 59.1 °F | 49.33 in. |
| Average First Frost Date | Oct. 21 - Oct. 31 |
| Average Last Frost Date | Apr. 11 - Apr. 20 |
| Average Days With Frost | 125-150 Days |
| Plant Hardiness Zone | Zone 6b : -5°F to 0°F |
| Plant Hardiness Zone - 2012 | Zone 6a : -10°F to -5°F |
| Current Drought Conditions | Moderate Drought |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |