Frost Dates for 11749 — Islandia, New York

Half of springs at Riverhead Rsch Farm, NY see their last 32°F night by April 6; only one in ten is past it by March 27, and one in ten still has one after April 19. Planting tender crops after April 12 leaves a 30% risk of a frost on them, after April 15 20%, and after April 19 10%. The 13 days between the even-odds date and the one-in-ten date is narrower than at 83% of the 173 New York stations behind this site's ZIP pages.

In fall the first 32°F night comes by November 9 in half of years, as early as October 28 one year in ten, and holds off past November 22 one year in ten. A hard freeze of 28°F follows 12 days later, around November 21; in spring the one-in-ten date for 28°F is April 7, 12 days before the 32°F one. The freeze-free season lasts 215 days in a typical year, longer than at 92% of the 173 New York stations; it reaches 233 days one year in ten and falls short of 198 one year in ten. On average 86 nights a year drop to 32°F or below. Nights of 36°F, when frost can still settle on leaves in low, open spots, continue 14 days longer, to about April 20, and return around October 28. Severe cold of 16°F or below comes in 99% of winters, usually between January 1 and February 23.

July is the warmest month at Riverhead Rsch Farm, NY, averaging 84°F by day and 67°F at night; January is the coldest at 40°F and 26°F. A freezing night is all but certain in every month from November to March (a 90% chance or more). From May to September the chance of a 32°F night stays under 10% each month. In spring, April still brings one in 78% of years.

Warmth for growing adds up to 3,416 growing degree days a year (base 50°F), more than at 94% of the 173 New York stations. 30% of them (1,035) have built up by the end of June, and July adds the most, 787. Precipitation totals 47.3 inches a year, most in March (4.7") and least in July (3.1"); May to September bring 39% of it.

The nearest other station, Baiting Hollow, NY, 5 miles west of Islandia, has a last frost 18 days later (April 24), a first frost 15 days earlier (October 25), a season 33 days shorter.

The first measurable snow (0.1 inch or more) in Islandia usually arrives around December 17, and the last of the season around March 18. Those are the middle dates across the winters of 1991–2020 at Riverhead Rsch Farm, NY, 5 miles away: half of years saw snow earlier, half later. Every one of those winters saw snow. The last 32°F night of spring typically comes 19 days after the last snow.

ZIP 11749 is 5 miles from Riverhead Rsch Farm, NY, which stands at 100 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 1 other ZIP code shares the station; its figures are presented in full for 11901 (Riverhead). The 2023 USDA Plant Hardiness Zone Map lists ZIP 11749 in zone 7b, the band where the coldest night of the year averaged 5 to 10°F (-15.0 to -12.2°C) over 1991–2020; a zone describes winter lows, not frost dates.