Washington Mills, New York has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 3.2 °C (low) to 14 °C (high). Annual precipitation averages 1215.6 Millimeters. Washington Mills is located in USDA Plant Hardiness Zone 5b. 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 | -10.1 °C | -0.8 °C | 78.99 mm |
| February | -9.4 °C | 0.4 °C | 70.87 mm |
| March | -5 °C | 5 °C | 89.41 mm |
| April | 1.5 °C | 13.4 °C | 103.63 mm |
| May | 7.8 °C | 20.7 °C | 100.84 mm |
| June | 13.1 °C | 25.4 °C | 122.43 mm |
| July | 15.7 °C | 27.9 °C | 121.92 mm |
| August | 14.9 °C | 26.9 °C | 111.25 mm |
| September | 10.9 °C | 22.9 °C | 104.39 mm |
| October | 5 °C | 15.6 °C | 116.84 mm |
| November | -0.4 °C | 8.3 °C | 101.85 mm |
| December | -5.8 °C | 2.1 °C | 93.22 mm |
| Annual | 3.2 °C | 14 °C | 1215.64 mm |
| Average First Frost Date | Oct. 1 - Oct. 10 |
| Average Last Frost Date | May 1 - May 10 |
| 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 |