Clarendon, Pennsylvania has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 2.2 °C (low) to 13.8 °C (high). Annual precipitation averages 1197.9 Millimeters. Clarendon 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 | -9.4 °C | -0.4 °C | 91.69 mm |
| February | -9.3 °C | 1.1 °C | 66.8 mm |
| March | -5.4 °C | 6.1 °C | 83.06 mm |
| April | 0.5 °C | 13.8 °C | 104.14 mm |
| May | 6.4 °C | 20.2 °C | 105.66 mm |
| June | 11.2 °C | 24.4 °C | 117.6 mm |
| July | 13.4 °C | 26.6 °C | 123.19 mm |
| August | 12.8 °C | 25.8 °C | 106.43 mm |
| September | 9.3 °C | 22.2 °C | 101.85 mm |
| October | 3.5 °C | 15.3 °C | 102.62 mm |
| November | -1.2 °C | 8.2 °C | 96.01 mm |
| December | -5.6 °C | 2.2 °C | 98.81 mm |
| Annual | 2.2 °C | 13.8 °C | 1197.86 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 5b : -26.1°C to -23.3°C |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |