Williamson, New York has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 4.4 °C (low) to 14.2 °C (high). Annual precipitation averages 976.6 Millimeters. Williamson is located in USDA Plant Hardiness Zone 6b. The growing season typically runs from the last frost around Apr. 21 - Apr. 30 through the first frost around Oct. 11 - Oct. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -7.8 °C | 0.6 °C | 73.15 mm |
| February | -7.1 °C | 1.2 °C | 57.91 mm |
| March | -3.6 °C | 5.9 °C | 67.56 mm |
| April | 2.2 °C | 13.1 °C | 78.23 mm |
| May | 8.2 °C | 20 °C | 81.03 mm |
| June | 13.5 °C | 24.1 °C | 87.63 mm |
| July | 16.7 °C | 27.3 °C | 90.68 mm |
| August | 15.9 °C | 26.6 °C | 90.17 mm |
| September | 12.2 °C | 23.2 °C | 86.11 mm |
| October | 6.2 °C | 15.8 °C | 100.33 mm |
| November | 0.8 °C | 9.4 °C | 84.07 mm |
| December | -4.1 °C | 3.3 °C | 79.76 mm |
| Annual | 4.4 °C | 14.2 °C | 976.63 mm |
| Average First Frost Date | Oct. 11 - Oct. 20 |
| Average Last Frost Date | Apr. 21 - Apr. 30 |
| Average Days With Frost | 125-150 Days |
| Plant Hardiness Zone | Zone 6b : -20.6°C to -17.8°C |
| Plant Hardiness Zone - 2012 | Zone 6a : -23.3°C to -20.6°C |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |