Grafton, New York has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 37.1 °F (low) to 55.2 °F (high). Annual precipitation averages 48.9 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 Oct. 1 - Oct. 10.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 14.0 °F | 29.8 °F | 3.21 in. |
| February | 15.3 °F | 32.7 °F | 2.71 in. |
| March | 22.9 °F | 40.7 °F | 3.5 in. |
| April | 34.2 °F | 54.7 °F | 3.76 in. |
| May | 45.7 °F | 66.5 °F | 4.14 in. |
| June | 54.6 °F | 74.2 °F | 5.11 in. |
| July | 59.1 °F | 78.8 °F | 4.77 in. |
| August | 57.7 °F | 76.9 °F | 4.56 in. |
| September | 50.6 °F | 70.1 °F | 4.42 in. |
| October | 40.5 °F | 58.0 °F | 5.21 in. |
| November | 29.7 °F | 45.5 °F | 3.6 in. |
| December | 20.7 °F | 34.8 °F | 3.95 in. |
| Annual | 37.1 °F | 55.2 °F | 48.94 in. |
| 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 5b : -15°F to -10°F |
| Plant Hardiness Zone - 2012 | Zone 5b : -15°F to -10°F |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |