Washington, Pennsylvania has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 4.6 °C (low) to 16.5 °C (high). Annual precipitation averages 1059.7 Millimeters. Washington is located in USDA Plant Hardiness Zone 6b. The growing season typically runs from the last frost around Apr. 21 - Apr. 30 through the first frost around Oct. 11 - Oct. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -6.8 °C | 2.8 °C | 81.53 mm |
| February | -6 °C | 4.4 °C | 60.71 mm |
| March | -2.1 °C | 9.7 °C | 86.11 mm |
| April | 3.3 °C | 16.8 °C | 83.57 mm |
| May | 8.9 °C | 22.1 °C | 110.24 mm |
| June | 13.8 °C | 26.3 °C | 116.59 mm |
| July | 16.1 °C | 28.6 °C | 105.41 mm |
| August | 15.2 °C | 27.9 °C | 88.65 mm |
| September | 11.4 °C | 24.5 °C | 90.93 mm |
| October | 5.1 °C | 17.8 °C | 80.26 mm |
| November | 0.1 °C | 11.2 °C | 75.69 mm |
| December | -3.9 °C | 5.3 °C | 80.01 mm |
| Annual | 4.6 °C | 16.5 °C | 1059.7 mm |
| Average First Frost Date | Oct. 11 - Oct. 20 |
| Average Last Frost Date | Apr. 21 - Apr. 30 |
| Average Days With Frost | 100-125 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 |