Sewell, New Jersey has a Humid Subtropical Climate climate (Köppen classification: Cfa). Average annual temperatures range from 8.2 °C (low) to 18.1 °C (high). Annual precipitation averages 1202.4 Millimeters. Sewell 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 | 5.2 °C | 95 mm |
| February | -2.7 °C | 6.6 °C | 71.88 mm |
| March | 1 °C | 10.9 °C | 114.3 mm |
| April | 6.7 °C | 17.7 °C | 90.42 mm |
| May | 12 °C | 23.1 °C | 95.25 mm |
| June | 17.3 °C | 28.2 °C | 109.47 mm |
| July | 20.4 °C | 30.5 °C | 118.36 mm |
| August | 19.6 °C | 29.4 °C | 116.33 mm |
| September | 15.8 °C | 25.8 °C | 104.65 mm |
| October | 9.1 °C | 19.2 °C | 100.84 mm |
| November | 3.4 °C | 13.2 °C | 78.23 mm |
| December | -0.5 °C | 7.9 °C | 107.7 mm |
| Annual | 8.2 °C | 18.1 °C | 1202.43 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 | Moderate Drought |
| Köppen Climate Classification | Cfa - Humid Subtropical Climate |