Washington, Maine has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 3 °C (low) to 12.5 °C (high). Annual precipitation averages 1252.2 Millimeters. Washington 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. 11 - Oct. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -11.1 °C | -1.7 °C | 96.27 mm |
| February | -9.9 °C | 0 °C | 85.6 mm |
| March | -4.7 °C | 4.4 °C | 103.12 mm |
| April | 1.6 °C | 11.2 °C | 112.78 mm |
| May | 7.4 °C | 17.8 °C | 93.98 mm |
| June | 12.6 °C | 22.5 °C | 111.51 mm |
| July | 15.8 °C | 25.6 °C | 85.34 mm |
| August | 15.3 °C | 25.1 °C | 87.12 mm |
| September | 11.2 °C | 21.1 °C | 101.85 mm |
| October | 5.2 °C | 14.2 °C | 141.22 mm |
| November | -0.6 °C | 7.6 °C | 116.08 mm |
| December | -6.4 °C | 1.6 °C | 117.35 mm |
| Annual | 3 °C | 12.5 °C | 1252.22 mm |
| Average First Frost Date | Oct. 11 - Oct. 20 |
| Average Last Frost Date | May 1 - May 10 |
| Average Days With Frost | 125-150 Days |
| Plant Hardiness Zone | Zone 5b : -26.1°C to -23.3°C |
| Plant Hardiness Zone - 2012 | Zone 5b : -26.1°C to -23.3°C |
| Current Drought Conditions | Abnormally Dry |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |