Washington, Indiana has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 7.2 °C (low) to 18.5 °C (high). Annual precipitation averages 1219.2 Millimeters. Washington is located in USDA Plant Hardiness Zone 6b. The growing season typically runs from the last frost around Apr. 11 - Apr. 20 through the first frost around Oct. 21 - Oct. 31.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -5.2 °C | 3.9 °C | 88.9 mm |
| February | -3.8 °C | 6.4 °C | 72.64 mm |
| March | 1 °C | 12.3 °C | 102.62 mm |
| April | 6.7 °C | 19.2 °C | 126.49 mm |
| May | 12.8 °C | 24.4 °C | 140.97 mm |
| June | 17.5 °C | 28.9 °C | 121.16 mm |
| July | 19.1 °C | 30.6 °C | 105.41 mm |
| August | 17.9 °C | 30 °C | 81.03 mm |
| September | 13.6 °C | 27.1 °C | 96.01 mm |
| October | 7.3 °C | 20.6 °C | 88.9 mm |
| November | 1.7 °C | 12.7 °C | 102.62 mm |
| December | -2.7 °C | 6.3 °C | 92.46 mm |
| Annual | 7.2 °C | 18.5 °C | 1219.21 mm |
| Average First Frost Date | Oct. 21 - Oct. 31 |
| Average Last Frost Date | Apr. 11 - Apr. 20 |
| Average Days With Frost | 75-100 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 | Normal |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |