Greencastle, Indiana has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 5.4 °C (low) to 16.3 °C (high). Annual precipitation averages 1168.7 Millimeters. Greencastle is located in USDA Plant Hardiness Zone 6a. 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 | -7.2 °C | 1.7 °C | 82.04 mm |
| February | -5.8 °C | 4.2 °C | 67.06 mm |
| March | -0.7 °C | 10.2 °C | 85.85 mm |
| April | 4.8 °C | 16.7 °C | 120.14 mm |
| May | 10.8 °C | 22.3 °C | 126.49 mm |
| June | 15.9 °C | 27 °C | 135.38 mm |
| July | 17.4 °C | 28.4 °C | 119.13 mm |
| August | 16.1 °C | 27.9 °C | 79.25 mm |
| September | 12.2 °C | 24.9 °C | 93.22 mm |
| October | 5.8 °C | 18.1 °C | 90.17 mm |
| November | 0.2 °C | 10.6 °C | 93.22 mm |
| December | -4.4 °C | 4.1 °C | 76.71 mm |
| Annual | 5.4 °C | 16.3 °C | 1168.66 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 6a : -23.3°C to -20.6°C |
| Plant Hardiness Zone - 2012 | Zone 6a : -23.3°C to -20.6°C |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |