Grier City, Pennsylvania has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 3.7 °C (low) to 15 °C (high). Annual precipitation averages 1384.3 Millimeters. Grier City is located in USDA Plant Hardiness Zone 6b. The growing season typically runs from the last frost around May 1 - May 10 through the first frost around Oct. 1 - Oct. 10.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -8.2 °C | 1.3 °C | 99.31 mm |
| February | -7.6 °C | 2.8 °C | 78.23 mm |
| March | -3.4 °C | 7.5 °C | 105.66 mm |
| April | 2.5 °C | 14.9 °C | 115.06 mm |
| May | 8.1 °C | 20.8 °C | 116.08 mm |
| June | 13.1 °C | 25 °C | 141.48 mm |
| July | 15.6 °C | 27.6 °C | 127.51 mm |
| August | 14.4 °C | 26.7 °C | 120.65 mm |
| September | 10.7 °C | 22.9 °C | 137.67 mm |
| October | 4.6 °C | 16.6 °C | 129.79 mm |
| November | -0.6 °C | 9.7 °C | 102.11 mm |
| December | -4.8 °C | 3.9 °C | 110.74 mm |
| Annual | 3.7 °C | 15 °C | 1384.29 mm |
| Average First Frost Date | Oct. 1 - Oct. 10 |
| Average Last Frost Date | May 1 - May 10 |
| Average Days With Frost | 100-125 Days |
| Plant Hardiness Zone | Zone 6b : -20.6°C to -17.8°C |
| Plant Hardiness Zone - 2012 | Zone 5b : -26.1°C to -23.3°C |
| Current Drought Conditions | Abnormally Dry |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |