Greencastle, Pennsylvania has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 6.6 °C (low) to 17.8 °C (high). Annual precipitation averages 1040.6 Millimeters. Greencastle is located in USDA Plant Hardiness Zone 7a. The growing season typically runs from the last frost around Apr. 11 - Apr. 20 through the first frost around Oct. 21 - Oct. 31.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -4.7 °C | 4.4 °C | 77.98 mm |
| February | -4.1 °C | 6.3 °C | 60.71 mm |
| March | -0.1 °C | 11.1 °C | 90.68 mm |
| April | 5.5 °C | 17.9 °C | 94.49 mm |
| May | 10.9 °C | 23 °C | 100.58 mm |
| June | 15.8 °C | 27.9 °C | 96.01 mm |
| July | 18.3 °C | 30.3 °C | 89.15 mm |
| August | 17.3 °C | 29.3 °C | 85.34 mm |
| September | 13.4 °C | 25.6 °C | 98.3 mm |
| October | 7.2 °C | 18.9 °C | 86.87 mm |
| November | 1.8 °C | 12.5 °C | 75.44 mm |
| December | -2.5 °C | 6.4 °C | 85.09 mm |
| Annual | 6.6 °C | 17.8 °C | 1040.64 mm |
| Average First Frost Date | Oct. 21 - Oct. 31 |
| Average Last Frost Date | Apr. 11 - Apr. 20 |
| Average Days With Frost | 100-125 Days |
| Plant Hardiness Zone | Zone 7a : -17.8°C to -15°C |
| Plant Hardiness Zone - 2012 | Zone 6b : -20.6°C to -17.8°C |
| Current Drought Conditions | Severe Drought |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |