New Castle, Pennsylvania has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 4.6 °C (low) to 16.5 °C (high). Annual precipitation averages 1047.7 Millimeters. 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 | -6.7 °C | 2.3 °C | 76.2 mm |
| February | -6.4 °C | 3.9 °C | 60.2 mm |
| March | -2.3 °C | 9.2 °C | 76.96 mm |
| April | 3.1 °C | 16.7 °C | 93.47 mm |
| May | 8.7 °C | 22.3 °C | 98.04 mm |
| June | 13.8 °C | 27.1 °C | 109.73 mm |
| July | 16.1 °C | 29.2 °C | 114.55 mm |
| August | 15.3 °C | 28.5 °C | 93.47 mm |
| September | 11.5 °C | 24.9 °C | 95 mm |
| October | 5.4 °C | 18.1 °C | 79.76 mm |
| November | 0.5 °C | 10.9 °C | 72.64 mm |
| December | -3.6 °C | 4.9 °C | 77.72 mm |
| Annual | 4.6 °C | 16.5 °C | 1047.74 mm |
| 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 : -20.6°C to -17.8°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 |