Holtsville, New York has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 7.2 °C (low) to 16.3 °C (high). Annual precipitation averages 1283.2 Millimeters. Holtsville is located in USDA Plant Hardiness Zone 7b. 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 | -4.3 °C | 4.2 °C | 99.57 mm |
| February | -3.7 °C | 5.2 °C | 91.69 mm |
| March | -0.2 °C | 8.9 °C | 129.79 mm |
| April | 4.9 °C | 14.8 °C | 109.73 mm |
| May | 10.3 °C | 20.3 °C | 100.08 mm |
| June | 15.8 °C | 25.3 °C | 111 mm |
| July | 19.2 °C | 28.4 °C | 85.34 mm |
| August | 18.5 °C | 27.4 °C | 105.16 mm |
| September | 14.8 °C | 24 °C | 101.85 mm |
| October | 8.7 °C | 17.9 °C | 123.7 mm |
| November | 3.1 °C | 12 °C | 98.04 mm |
| December | -1.2 °C | 7.2 °C | 127.25 mm |
| Annual | 7.2 °C | 16.3 °C | 1283.2 mm |
| Average First Frost Date | Oct. 21 - Oct. 31 |
| Average Last Frost Date | Apr. 11 - Apr. 20 |
| 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 |