Chatham, New York has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 3.3 °C (low) to 15 °C (high). Annual precipitation averages 1062.5 Millimeters. Chatham is located in USDA Plant Hardiness Zone 6a. 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 | -9.4 °C | 0.6 °C | 70.61 mm |
| February | -8.6 °C | 2.3 °C | 57.91 mm |
| March | -4.1 °C | 7.2 °C | 75.44 mm |
| April | 1.9 °C | 14.9 °C | 80.26 mm |
| May | 7.9 °C | 21.4 °C | 92.2 mm |
| June | 13 °C | 25.6 °C | 102.36 mm |
| July | 15.7 °C | 28.2 °C | 101.35 mm |
| August | 14.9 °C | 27.3 °C | 95 mm |
| September | 10.5 °C | 23.3 °C | 118.62 mm |
| October | 4.4 °C | 16.3 °C | 104.39 mm |
| November | -0.6 °C | 9.6 °C | 73.66 mm |
| December | -5.5 °C | 3.3 °C | 90.68 mm |
| Annual | 3.3 °C | 15 °C | 1062.48 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 6a : -23.3°C to -20.6°C |
| Plant Hardiness Zone - 2012 | Zone 5b : -26.1°C to -23.3°C |
| Current Drought Conditions | Abnormally Dry |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |