Iselin, New Jersey has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 7.1 °C (low) to 17.8 °C (high). Annual precipitation averages 1232.7 Millimeters. Iselin is located in USDA Plant Hardiness Zone 7a. The growing season typically runs from the last frost around Apr. 11 - Apr. 20 through the first frost around Oct. 21 - Oct. 31.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -4.6 °C | 4.5 °C | 90.42 mm |
| February | -3.7 °C | 6 °C | 71.88 mm |
| March | 0.1 °C | 10.5 °C | 106.68 mm |
| April | 5.7 °C | 17.3 °C | 98.81 mm |
| May | 11 °C | 22.7 °C | 100.58 mm |
| June | 16.2 °C | 27.7 °C | 116.08 mm |
| July | 19.2 °C | 30.4 °C | 126.75 mm |
| August | 18.4 °C | 29.4 °C | 113.54 mm |
| September | 14.4 °C | 25.7 °C | 108.46 mm |
| October | 7.9 °C | 19 °C | 107.95 mm |
| November | 2.5 °C | 12.9 °C | 85.6 mm |
| December | -1.6 °C | 7.3 °C | 105.92 mm |
| Annual | 7.1 °C | 17.8 °C | 1232.67 mm |
| Average First Frost Date | Oct. 21 - Oct. 31 |
| Average Last Frost Date | Apr. 11 - Apr. 20 |
| Average Days With Frost | 100-125 Days |
| Plant Hardiness Zone | Zone 7a : -17.8°C to -15°C |
| Plant Hardiness Zone - 2012 | Zone 6b : -20.6°C to -17.8°C |
| Current Drought Conditions | Moderate Drought |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |