New Castle, Indiana has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 40.7 °F (low) to 60.7 °F (high). Annual precipitation averages 44.6 Inches. 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 | 18.0 °F | 33.9 °F | 3.05 in. |
| February | 20.5 °F | 37.9 °F | 2.45 in. |
| March | 29.0 °F | 48.5 °F | 3.49 in. |
| April | 39.3 °F | 61.4 °F | 4.46 in. |
| May | 50.4 °F | 71.6 °F | 4.88 in. |
| June | 59.6 °F | 80.0 °F | 5.26 in. |
| July | 62.0 °F | 82.8 °F | 4.52 in. |
| August | 60.1 °F | 81.7 °F | 3.47 in. |
| September | 52.6 °F | 76.7 °F | 3.19 in. |
| October | 41.8 °F | 64.7 °F | 3.24 in. |
| November | 31.9 °F | 50.5 °F | 3.44 in. |
| December | 23.7 °F | 38.6 °F | 3.12 in. |
| Annual | 40.7 °F | 60.7 °F | 44.57 in. |
| 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 : -10°F to -5°F |
| Plant Hardiness Zone - 2012 | Zone 5b : -15°F to -10°F |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |