Addison, Pennsylvania has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 3.8 °C (low) to 15.2 °C (high). Annual precipitation averages 1222.3 Millimeters. Addison is located in USDA Plant Hardiness Zone 6a. The growing season typically runs from the last frost around May 11 - May 20 through the first frost around Oct. 11 - Oct. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -7.3 °C | 1.8 °C | 95.25 mm |
| February | -6.6 °C | 3.7 °C | 88.14 mm |
| March | -2.8 °C | 8.5 °C | 102.87 mm |
| April | 2.7 °C | 15.8 °C | 104.39 mm |
| May | 8.2 °C | 20.9 °C | 124.21 mm |
| June | 12.8 °C | 25.1 °C | 124.71 mm |
| July | 15.1 °C | 27.1 °C | 117.6 mm |
| August | 14.2 °C | 26.3 °C | 103.89 mm |
| September | 10.3 °C | 23 °C | 98.04 mm |
| October | 4.5 °C | 16.7 °C | 84.84 mm |
| November | -0.8 °C | 9.8 °C | 80.77 mm |
| December | -4.7 °C | 4.1 °C | 97.54 mm |
| Annual | 3.8 °C | 15.2 °C | 1222.25 mm |
| Average First Frost Date | Oct. 11 - Oct. 20 |
| Average Last Frost Date | May 11 - May 20 |
| 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 | Normal |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |