Julian, Pennsylvania has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 3.9 °C (low) to 15.7 °C (high). Annual precipitation averages 1072.1 Millimeters. Julian 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. 21 - Oct. 31.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -7.6 °C | 1.8 °C | 74.42 mm |
| February | -7 °C | 3.5 °C | 61.47 mm |
| March | -3.2 °C | 8.4 °C | 85.34 mm |
| April | 2.5 °C | 15.9 °C | 91.69 mm |
| May | 8.3 °C | 21.7 °C | 101.35 mm |
| June | 13.3 °C | 26 °C | 102.87 mm |
| July | 15.7 °C | 28.4 °C | 100.84 mm |
| August | 14.8 °C | 27.4 °C | 99.82 mm |
| September | 10.6 °C | 23.6 °C | 104.65 mm |
| October | 4.4 °C | 16.9 °C | 94.74 mm |
| November | -0.7 °C | 10.3 °C | 74.93 mm |
| December | -4.6 °C | 4.2 °C | 80.01 mm |
| Annual | 3.9 °C | 15.7 °C | 1072.13 mm |
| Average First Frost Date | Oct. 21 - Oct. 31 |
| 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 6b : -20.6°C to -17.8°C |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |