Iselin, New Jersey has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 44.8 °F (low) to 64 °F (high). Annual precipitation averages 48.5 Inches. 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 | 23.8 °F | 40.1 °F | 3.56 in. |
| February | 25.3 °F | 42.8 °F | 2.83 in. |
| March | 32.1 °F | 50.9 °F | 4.2 in. |
| April | 42.2 °F | 63.1 °F | 3.89 in. |
| May | 51.8 °F | 72.9 °F | 3.96 in. |
| June | 61.1 °F | 81.9 °F | 4.57 in. |
| July | 66.6 °F | 86.8 °F | 4.99 in. |
| August | 65.1 °F | 84.9 °F | 4.47 in. |
| September | 58.0 °F | 78.2 °F | 4.27 in. |
| October | 46.2 °F | 66.2 °F | 4.25 in. |
| November | 36.5 °F | 55.3 °F | 3.37 in. |
| December | 29.2 °F | 45.2 °F | 4.17 in. |
| Annual | 44.8 °F | 64 °F | 48.53 in. |
| 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 : 0°F to 5°F |
| Plant Hardiness Zone - 2012 | Zone 6b : -5°F to 0°F |
| Current Drought Conditions | Severe Drought |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |