Chestertown, New York has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 1.1 °C (low) to 13 °C (high). Annual precipitation averages 1125.2 Millimeters. Chestertown is located in USDA Plant Hardiness Zone 5a. 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 | -12.7 °C | -1.6 °C | 83.82 mm |
| February | -12.1 °C | -0.1 °C | 66.55 mm |
| March | -7 °C | 4.6 °C | 88.65 mm |
| April | -0.8 °C | 12.4 °C | 97.28 mm |
| May | 6.3 °C | 19.7 °C | 95.76 mm |
| June | 11.3 °C | 24.3 °C | 114.55 mm |
| July | 14.3 °C | 26.8 °C | 104.39 mm |
| August | 13.3 °C | 25.7 °C | 93.98 mm |
| September | 9.1 °C | 21.6 °C | 87.88 mm |
| October | 2.7 °C | 14.2 °C | 107.7 mm |
| November | -2.9 °C | 6.9 °C | 86.87 mm |
| December | -8.5 °C | 0.9 °C | 97.79 mm |
| Annual | 1.1 °C | 13 °C | 1125.22 mm |
| 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 5a : -28.9°C to -26.1°C |
| Plant Hardiness Zone - 2012 | Zone 4b : -31.7°C to -28.9°C |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |