Fairfield, Pennsylvania has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 5.9 °C (low) to 17.3 °C (high). Annual precipitation averages 1160.3 Millimeters. Fairfield is located in USDA Plant Hardiness Zone 7a. 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 | -5.6 °C | 3.8 °C | 86.61 mm |
| February | -4.8 °C | 5.7 °C | 68.33 mm |
| March | -0.9 °C | 10.3 °C | 99.06 mm |
| April | 4.7 °C | 17.3 °C | 98.3 mm |
| May | 10.3 °C | 22.4 °C | 110.74 mm |
| June | 15.3 °C | 27.2 °C | 104.14 mm |
| July | 17.8 °C | 29.8 °C | 99.06 mm |
| August | 16.8 °C | 28.8 °C | 95.5 mm |
| September | 12.9 °C | 25.1 °C | 123.44 mm |
| October | 6.4 °C | 18.6 °C | 99.31 mm |
| November | 1 °C | 12.2 °C | 83.31 mm |
| December | -2.9 °C | 6.2 °C | 92.46 mm |
| Annual | 5.9 °C | 17.3 °C | 1160.26 mm |
| Average First Frost Date | Oct. 21 - Oct. 31 |
| Average Last Frost Date | Apr. 11 - Apr. 20 |
| Average Days With Frost | 100-125 Days |
| Plant Hardiness Zone | Zone 7a : -17.8°C to -15°C |
| Plant Hardiness Zone - 2012 | Zone 6b : -20.6°C to -17.8°C |
| Current Drought Conditions | Moderate Drought |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |