Thornwood, New York has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 6 °C (low) to 16.5 °C (high). Annual precipitation averages 1283 Millimeters. Thornwood is located in USDA Plant Hardiness Zone 7a. 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 | -5.9 °C | 3.1 °C | 97.79 mm |
| February | -5.1 °C | 4.7 °C | 70.87 mm |
| March | -1.3 °C | 9.1 °C | 104.39 mm |
| April | 4.5 °C | 16.1 °C | 99.57 mm |
| May | 9.9 °C | 21.8 °C | 93.22 mm |
| June | 15.1 °C | 26.5 °C | 119.63 mm |
| July | 18 °C | 29.2 °C | 113.28 mm |
| August | 17.2 °C | 28.1 °C | 125.48 mm |
| September | 13.2 °C | 24.3 °C | 122.17 mm |
| October | 6.9 °C | 17.8 °C | 120.4 mm |
| November | 1.7 °C | 11.7 °C | 107.44 mm |
| December | -2.4 °C | 5.9 °C | 108.71 mm |
| Annual | 6 °C | 16.5 °C | 1282.95 mm |
| Average First Frost Date | Oct. 21 - Oct. 31 |
| Average Last Frost Date | Apr. 11 - Apr. 20 |
| Average Days With Frost | 75-100 Days |
| Plant Hardiness Zone | Zone 7a : -17.8°C to -15°C |
| Plant Hardiness Zone - 2012 | Zone 7a : -17.8°C to -15°C |
| Current Drought Conditions | Moderate Drought |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |