Unionville, New York has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 3.9 °C (low) to 15.7 °C (high). Annual precipitation averages 1175.3 Millimeters. Unionville is located in USDA Plant Hardiness Zone 6b. 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 | -8.3 °C | 1.8 °C | 79.76 mm |
| February | -7.6 °C | 3.6 °C | 66.29 mm |
| March | -3.4 °C | 8.3 °C | 97.54 mm |
| April | 2.6 °C | 15.5 °C | 97.79 mm |
| May | 8.3 °C | 21.5 °C | 90.17 mm |
| June | 13.4 °C | 25.9 °C | 122.43 mm |
| July | 16.1 °C | 28.6 °C | 100.33 mm |
| August | 15.2 °C | 27.4 °C | 118.11 mm |
| September | 11.2 °C | 23.8 °C | 110.24 mm |
| October | 4.8 °C | 17.2 °C | 107.7 mm |
| November | -0.7 °C | 10.7 °C | 83.82 mm |
| December | -4.8 °C | 4.6 °C | 101.09 mm |
| Annual | 3.9 °C | 15.7 °C | 1175.27 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 6b : -20.6°C to -17.8°C |
| Plant Hardiness Zone - 2012 | Zone 6a : -23.3°C to -20.6°C |
| Current Drought Conditions | Abnormally Dry |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |