Mercer, Pennsylvania has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 39 °F (low) to 59.6 °F (high). Annual precipitation averages 45 Inches. Mercer 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. 1 - Oct. 10.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 17.5 °F | 34.2 °F | 3.34 in. |
| February | 18.2 °F | 37.2 °F | 2.56 in. |
| March | 25.9 °F | 46.5 °F | 3.3 in. |
| April | 36.6 °F | 60.0 °F | 4.06 in. |
| May | 47.0 °F | 70.3 °F | 3.76 in. |
| June | 55.9 °F | 78.2 °F | 4.97 in. |
| July | 59.7 °F | 82.2 °F | 4.8 in. |
| August | 58.5 °F | 80.9 °F | 3.83 in. |
| September | 51.7 °F | 74.8 °F | 4.22 in. |
| October | 41.0 °F | 62.5 °F | 3.36 in. |
| November | 32.0 °F | 49.6 °F | 3.34 in. |
| December | 23.8 °F | 38.9 °F | 3.48 in. |
| Annual | 39 °F | 59.6 °F | 45.02 in. |
| Average First Frost Date | Oct. 1 - Oct. 10 |
| 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 |