New Gretna, New Jersey has a Humid Subtropical Climate climate (Köppen classification: Cfa). Average annual temperatures range from 7.3 °C (low) to 17.8 °C (high). Annual precipitation averages 1226.3 Millimeters. New Gretna is located in USDA Plant Hardiness Zone 7a. 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 | -4.2 °C | 5.8 °C | 95.25 mm |
| February | -3.7 °C | 6.9 °C | 75.44 mm |
| March | 0.2 °C | 10.3 °C | 120.14 mm |
| April | 5.6 °C | 16.7 °C | 89.92 mm |
| May | 10.9 °C | 21.9 °C | 91.69 mm |
| June | 16.3 °C | 27.1 °C | 100.58 mm |
| July | 19.3 °C | 29.6 °C | 125.98 mm |
| August | 18.4 °C | 28.6 °C | 126.24 mm |
| September | 15.1 °C | 25.3 °C | 91.19 mm |
| October | 8.6 °C | 19.4 °C | 107.95 mm |
| November | 2.9 °C | 13.7 °C | 85.85 mm |
| December | -1.4 °C | 8.4 °C | 116.08 mm |
| Annual | 7.3 °C | 17.8 °C | 1226.31 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 7a : -17.8°C to -15°C |
| Plant Hardiness Zone - 2012 | Zone 7a : -17.8°C to -15°C |
| Current Drought Conditions | Severe Drought |
| Köppen Climate Classification | Cfa - Humid Subtropical Climate |