Washington, Connecticut has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 3.7 °C (low) to 15.2 °C (high). Annual precipitation averages 1265.4 Millimeters. Washington is located in USDA Plant Hardiness Zone 6a. The growing season typically runs from the last frost around Apr. 21 - Apr. 30 through the first frost around Oct. 1 - Oct. 10.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -8.6 °C | 1.8 °C | 86.36 mm |
| February | -7.6 °C | 3.4 °C | 72.9 mm |
| March | -3.7 °C | 7.7 °C | 103.38 mm |
| April | 2.1 °C | 14.8 °C | 96.77 mm |
| May | 7.8 °C | 20.7 °C | 102.36 mm |
| June | 12.9 °C | 25.1 °C | 114.3 mm |
| July | 15.9 °C | 27.7 °C | 118.36 mm |
| August | 15.2 °C | 26.8 °C | 121.92 mm |
| September | 11.2 °C | 22.7 °C | 114.55 mm |
| October | 4.8 °C | 16.4 °C | 128.52 mm |
| November | -0.4 °C | 10.4 °C | 96.27 mm |
| December | -5.1 °C | 4.3 °C | 109.73 mm |
| Annual | 3.7 °C | 15.2 °C | 1265.42 mm |
| Average First Frost Date | Oct. 1 - Oct. 10 |
| Average Last Frost Date | Apr. 21 - Apr. 30 |
| Average Days With Frost | 125-150 Days |
| Plant Hardiness Zone | Zone 6a : -23.3°C to -20.6°C |
| Plant Hardiness Zone - 2012 | Zone 6a : -23.3°C to -20.6°C |
| Current Drought Conditions | Moderate Drought |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |