Plains, Pennsylvania has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 4.5 °C (low) to 16 °C (high). Annual precipitation averages 1081 Millimeters. Plains is located in USDA Plant Hardiness Zone 6b. The growing season typically runs from the last frost around Apr. 21 - Apr. 30 through the first frost around Oct. 11 - Oct. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -7.4 °C | 1.9 °C | 66.29 mm |
| February | -6.8 °C | 3.6 °C | 60.96 mm |
| March | -2.7 °C | 8.3 °C | 68.33 mm |
| April | 3.1 °C | 15.7 °C | 91.19 mm |
| May | 8.9 °C | 22 °C | 90.68 mm |
| June | 13.8 °C | 26.4 °C | 116.59 mm |
| July | 16.3 °C | 29.2 °C | 111.25 mm |
| August | 15.4 °C | 28 °C | 97.79 mm |
| September | 11.4 °C | 24.2 °C | 117.6 mm |
| October | 5.3 °C | 17.2 °C | 108.2 mm |
| November | 0.3 °C | 10.7 °C | 73.15 mm |
| December | -4.1 °C | 4.7 °C | 78.99 mm |
| Annual | 4.5 °C | 16 °C | 1081.02 mm |
| Average First Frost Date | Oct. 11 - Oct. 20 |
| Average Last Frost Date | Apr. 21 - Apr. 30 |
| Average Days With Frost | 100-125 Days |
| Plant Hardiness Zone | Zone 6b : -20.6°C to -17.8°C |
| Plant Hardiness Zone - 2012 | Zone 6a : -23.3°C to -20.6°C |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |