West Middlesex, Pennsylvania has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 40.3 °F (low) to 61.7 °F (high). Annual precipitation averages 41.6 Inches. West Middlesex 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 | 19.5 °F | 35.8 °F | 2.91 in. |
| February | 20.2 °F | 38.8 °F | 2.3 in. |
| March | 27.7 °F | 48.1 °F | 2.94 in. |
| April | 37.7 °F | 62.2 °F | 3.77 in. |
| May | 48.0 °F | 72.7 °F | 3.85 in. |
| June | 56.9 °F | 81.0 °F | 4.47 in. |
| July | 61.1 °F | 84.7 °F | 4.48 in. |
| August | 59.4 °F | 83.3 °F | 3.62 in. |
| September | 52.6 °F | 76.9 °F | 3.97 in. |
| October | 41.9 °F | 64.6 °F | 3.18 in. |
| November | 33.3 °F | 51.4 °F | 2.98 in. |
| December | 25.6 °F | 40.6 °F | 3.14 in. |
| Annual | 40.3 °F | 61.7 °F | 41.61 in. |
| 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 : -10°F to -5°F |
| Plant Hardiness Zone - 2012 | Zone 6a : -10°F to -5°F |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |