Defiance, Pennsylvania has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 4.5 °C (low) to 16 °C (high). Annual precipitation averages 1064 Millimeters. Defiance is located in USDA Plant Hardiness Zone 6b. 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 | -6.8 °C | 2.4 °C | 74.68 mm |
| February | -6.2 °C | 4.2 °C | 60.2 mm |
| March | -2.4 °C | 8.8 °C | 91.44 mm |
| April | 3.3 °C | 16.3 °C | 93.22 mm |
| May | 8.9 °C | 21.6 °C | 103.89 mm |
| June | 13.7 °C | 26.1 °C | 99.31 mm |
| July | 16.1 °C | 28.6 °C | 102.62 mm |
| August | 15.2 °C | 27.7 °C | 88.14 mm |
| September | 11.3 °C | 23.9 °C | 102.62 mm |
| October | 5 °C | 17.4 °C | 85.85 mm |
| November | -0.3 °C | 10.7 °C | 80.52 mm |
| December | -4.1 °C | 4.7 °C | 81.53 mm |
| Annual | 4.5 °C | 16 °C | 1064.02 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 6b : -20.6°C to -17.8°C |
| Plant Hardiness Zone - 2012 | Zone 6b : -20.6°C to -17.8°C |
| Current Drought Conditions | Abnormally Dry |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |