New Castle, Delaware has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 46.1 °F (low) to 63.9 °F (high). Annual precipitation averages 46.8 Inches. New Castle is located in USDA Plant Hardiness Zone 7b. The growing season typically runs from the last frost around Apr. 1 - Apr. 10 through the first frost around Nov. 1 - Nov. 10.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 25.0 °F | 40.6 °F | 3.44 in. |
| February | 26.2 °F | 43.2 °F | 2.9 in. |
| March | 33.3 °F | 51.0 °F | 4.27 in. |
| April | 43.7 °F | 62.9 °F | 3.64 in. |
| May | 53.6 °F | 72.4 °F | 3.72 in. |
| June | 63.0 °F | 81.4 °F | 4.63 in. |
| July | 68.2 °F | 85.9 °F | 4.57 in. |
| August | 66.6 °F | 84.0 °F | 4.16 in. |
| September | 59.7 °F | 78.0 °F | 4.27 in. |
| October | 47.2 °F | 66.3 °F | 3.92 in. |
| November | 37.0 °F | 55.4 °F | 3.13 in. |
| December | 30.0 °F | 45.6 °F | 4.14 in. |
| Annual | 46.1 °F | 63.9 °F | 46.79 in. |
| Average First Frost Date | Nov. 1 - Nov. 10 |
| Average Last Frost Date | Apr. 1 - Apr. 10 |
| Average Days With Frost | 75-100 Days |
| Plant Hardiness Zone | Zone 7b : 5°F to 10°F |
| Plant Hardiness Zone - 2012 | Zone 7a : 0°F to 5°F |
| Current Drought Conditions | Severe Drought |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |