Westernville, New York has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 2.9 °C (low) to 13.6 °C (high). Annual precipitation averages 1317 Millimeters. Westernville is located in USDA Plant Hardiness Zone 5b. 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 | -10.7 °C | -1.2 °C | 98.3 mm |
| February | -10.1 °C | 0.2 °C | 80.52 mm |
| March | -5.4 °C | 4.7 °C | 91.69 mm |
| April | 1.2 °C | 12.9 °C | 107.95 mm |
| May | 7.5 °C | 20.2 °C | 117.35 mm |
| June | 12.8 °C | 24.8 °C | 124.46 mm |
| July | 15.5 °C | 27.3 °C | 117.86 mm |
| August | 14.7 °C | 26.3 °C | 104.39 mm |
| September | 10.7 °C | 22.5 °C | 111.76 mm |
| October | 4.8 °C | 15.1 °C | 136.65 mm |
| November | -0.6 °C | 8.2 °C | 112.27 mm |
| December | -6.1 °C | 1.8 °C | 113.79 mm |
| Annual | 2.9 °C | 13.6 °C | 1316.99 mm |
| Average First Frost Date | Oct. 11 - Oct. 20 |
| Average Last Frost Date | Apr. 21 - Apr. 30 |
| Average Days With Frost | 150-180 Days |
| Plant Hardiness Zone | Zone 5b : -26.1°C to -23.3°C |
| Plant Hardiness Zone - 2012 | Zone 5a : -28.9°C to -26.1°C |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |