Hewitt, New Jersey has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 4.7 °C (low) to 16.3 °C (high). Annual precipitation averages 1304.5 Millimeters. Hewitt is located in USDA Plant Hardiness Zone 7a. The growing season typically runs from the last frost around Apr. 21 - Apr. 30 through the first frost around Oct. 11 - Oct. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -6.9 °C | 2.7 °C | 100.58 mm |
| February | -6.4 °C | 4.4 °C | 75.69 mm |
| March | -2.3 °C | 8.6 °C | 113.03 mm |
| April | 3.6 °C | 15.8 °C | 100.08 mm |
| May | 8.7 °C | 21.6 °C | 99.57 mm |
| June | 13.9 °C | 26.2 °C | 125.98 mm |
| July | 16.4 °C | 29.3 °C | 106.93 mm |
| August | 15.9 °C | 28.3 °C | 128.02 mm |
| September | 11.6 °C | 24.6 °C | 122.68 mm |
| October | 5.4 °C | 17.6 °C | 113.79 mm |
| November | 0.3 °C | 11.4 °C | 101.85 mm |
| December | -3.6 °C | 5.3 °C | 116.33 mm |
| Annual | 4.7 °C | 16.3 °C | 1304.53 mm |
| Average First Frost Date | Oct. 11 - Oct. 20 |
| Average Last Frost Date | Apr. 21 - Apr. 30 |
| Average Days With Frost | 125-150 Days |
| Plant Hardiness Zone | Zone 7a : -17.8°C to -15°C |
| Plant Hardiness Zone - 2012 | Zone 6a : -23.3°C to -20.6°C |
| Current Drought Conditions | Abnormally Dry |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |