Islip, New York has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 7.6 °C (low) to 16.2 °C (high). Annual precipitation averages 1256.5 Millimeters. Islip 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 Oct. 21 - Oct. 31.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -3.8 °C | 4.1 °C | 99.06 mm |
| February | -3.2 °C | 5.1 °C | 87.88 mm |
| March | 0.1 °C | 8.7 °C | 124.71 mm |
| April | 5.3 °C | 14.7 °C | 109.22 mm |
| May | 10.6 °C | 20.1 °C | 95.25 mm |
| June | 16.1 °C | 25.2 °C | 107.19 mm |
| July | 19.6 °C | 28.2 °C | 86.11 mm |
| August | 18.9 °C | 27.8 °C | 105.16 mm |
| September | 15.3 °C | 23.7 °C | 99.57 mm |
| October | 9.2 °C | 17.6 °C | 123.44 mm |
| November | 3.7 °C | 12.2 °C | 94.49 mm |
| December | -0.5 °C | 7.1 °C | 124.46 mm |
| Annual | 7.6 °C | 16.2 °C | 1256.54 mm |
| Average First Frost Date | Oct. 21 - Oct. 31 |
| 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 | Dfa - Humid Continental Hot Summers With Year Around Precipitation |