Clarendon, Pennsylvania has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 35.9 °F (low) to 56.8 °F (high). Annual precipitation averages 47.2 Inches. 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 | 15.0 °F | 31.3 °F | 3.61 in. |
| February | 15.2 °F | 33.9 °F | 2.63 in. |
| March | 22.2 °F | 43.0 °F | 3.27 in. |
| April | 32.9 °F | 56.8 °F | 4.1 in. |
| May | 43.5 °F | 68.4 °F | 4.16 in. |
| June | 52.1 °F | 76.0 °F | 4.63 in. |
| July | 56.2 °F | 79.9 °F | 4.85 in. |
| August | 55.1 °F | 78.4 °F | 4.19 in. |
| September | 48.7 °F | 71.9 °F | 4.01 in. |
| October | 38.3 °F | 59.5 °F | 4.04 in. |
| November | 29.8 °F | 46.7 °F | 3.78 in. |
| December | 22.0 °F | 35.9 °F | 3.89 in. |
| Annual | 35.9 °F | 56.8 °F | 47.16 in. |
| 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 : -10°F to -5°F |
| Plant Hardiness Zone - 2012 | Zone 5b : -15°F to -10°F |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |