New Castle, Pennsylvania has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 40.3 °F (low) to 61.7 °F (high). Annual precipitation averages 41.3 Inches. New Castle is located in USDA Plant Hardiness Zone 6b. The growing season typically runs from the last frost around May 1 - May 10 through the first frost around Oct. 1 - Oct. 10.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 19.9 °F | 36.1 °F | 3.0 in. |
| February | 20.4 °F | 39.1 °F | 2.37 in. |
| March | 27.8 °F | 48.5 °F | 3.03 in. |
| April | 37.5 °F | 62.0 °F | 3.68 in. |
| May | 47.7 °F | 72.2 °F | 3.86 in. |
| June | 56.8 °F | 80.7 °F | 4.32 in. |
| July | 61.0 °F | 84.5 °F | 4.51 in. |
| August | 59.5 °F | 83.3 °F | 3.68 in. |
| September | 52.7 °F | 76.9 °F | 3.74 in. |
| October | 41.8 °F | 64.5 °F | 3.14 in. |
| November | 32.9 °F | 51.7 °F | 2.86 in. |
| December | 25.6 °F | 40.9 °F | 3.06 in. |
| Annual | 40.3 °F | 61.7 °F | 41.25 in. |
| Average First Frost Date | Oct. 1 - Oct. 10 |
| Average Last Frost Date | May 1 - May 10 |
| Average Days With Frost | 125-150 Days |
| Plant Hardiness Zone | Zone 6b : -5°F to 0°F |
| Plant Hardiness Zone - 2012 | Zone 6a : -10°F to -5°F |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |