Penns Grove, New Jersey has a Humid Subtropical Climate climate (Köppen classification: Cfa). Average annual temperatures range from 8.3 °C (low) to 17.6 °C (high). Annual precipitation averages 1192.8 Millimeters. Penns Grove 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 | -3.4 °C | 4.8 °C | 89.66 mm |
| February | -2.7 °C | 6.1 °C | 74.17 mm |
| March | 1.1 °C | 10.3 °C | 110.24 mm |
| April | 6.9 °C | 17.1 °C | 95 mm |
| May | 12.3 °C | 22.3 °C | 95 mm |
| June | 17.7 °C | 27.4 °C | 114.81 mm |
| July | 20.7 °C | 29.8 °C | 120.9 mm |
| August | 19.8 °C | 28.9 °C | 109.73 mm |
| September | 15.9 °C | 25.5 °C | 106.68 mm |
| October | 9.1 °C | 18.9 °C | 96.01 mm |
| November | 3.4 °C | 12.9 °C | 75.95 mm |
| December | -0.7 °C | 7.6 °C | 104.65 mm |
| Annual | 8.3 °C | 17.6 °C | 1192.8 mm |
| 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 : -15°C to -12.2°C |
| Plant Hardiness Zone - 2012 | Zone 7a : -17.8°C to -15°C |
| Current Drought Conditions | Abnormally Dry |
| Köppen Climate Classification | Cfa - Humid Subtropical Climate |