New Castle, Indiana has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 4.8 °C (low) to 16 °C (high). Annual precipitation averages 1132.1 Millimeters. New Castle 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 | -7.8 °C | 1.1 °C | 77.47 mm |
| February | -6.4 °C | 3.3 °C | 62.23 mm |
| March | -1.7 °C | 9.2 °C | 88.65 mm |
| April | 4.1 °C | 16.3 °C | 113.28 mm |
| May | 10.2 °C | 22 °C | 123.95 mm |
| June | 15.3 °C | 26.7 °C | 133.6 mm |
| July | 16.7 °C | 28.2 °C | 114.81 mm |
| August | 15.6 °C | 27.6 °C | 88.14 mm |
| September | 11.4 °C | 24.8 °C | 81.03 mm |
| October | 5.4 °C | 18.2 °C | 82.3 mm |
| November | -0.1 °C | 10.3 °C | 87.38 mm |
| December | -4.6 °C | 3.7 °C | 79.25 mm |
| Annual | 4.8 °C | 16 °C | 1132.09 mm |
| Average First Frost Date | Oct. 11 - Oct. 20 |
| Average Last Frost Date | Apr. 21 - Apr. 30 |
| Average Days With Frost | 125-150 Days |
| Plant Hardiness Zone | Zone 6a : -23.3°C to -20.6°C |
| Plant Hardiness Zone - 2012 | Zone 5b : -26.1°C to -23.3°C |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |