Clark, Pennsylvania has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 4.4 °C (low) to 16.2 °C (high). Annual precipitation averages 1075.4 Millimeters. Clark is located in USDA Plant Hardiness Zone 6a. 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 | -7.2 °C | 1.9 °C | 75.69 mm |
| February | -6.8 °C | 3.6 °C | 58.67 mm |
| March | -2.6 °C | 8.7 °C | 76.2 mm |
| April | 2.9 °C | 16.4 °C | 98.04 mm |
| May | 8.7 °C | 22.3 °C | 98.3 mm |
| June | 13.7 °C | 26.9 °C | 115.06 mm |
| July | 15.9 °C | 28.9 °C | 114.55 mm |
| August | 14.9 °C | 28.2 °C | 93.73 mm |
| September | 11.3 °C | 24.7 °C | 102.87 mm |
| October | 5.2 °C | 17.8 °C | 83.82 mm |
| November | 0.5 °C | 10.6 °C | 77.72 mm |
| December | -3.8 °C | 4.6 °C | 80.77 mm |
| Annual | 4.4 °C | 16.2 °C | 1075.42 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 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 |