Frost Dates for 06830 — Greenwich, Connecticut

Half of springs at Westchester Co Airport, NY see their last 32°F night by April 12; only one in ten is past it by April 1, and one in ten still has one after April 27. Planting tender crops after April 18 leaves a 30% risk of a frost on them, after April 21 20%, and after April 27 10%. The 15 days between the even-odds date and the one-in-ten date is wider than at 50% of the 28 Connecticut stations behind this site's ZIP pages.

In fall the first 32°F night comes by October 31 in half of years, as early as October 15 one year in ten, and holds off past November 14 one year in ten. A hard freeze of 28°F follows 13 days later, around November 13; in spring the one-in-ten date for 28°F is April 13, 14 days before the 32°F one. The freeze-free season lasts 200 days in a typical year, longer than at 86% of the 28 Connecticut stations; it reaches 219 days one year in ten and falls short of 179 one year in ten. On average 105 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 26, and return around October 18. Severe cold of 16°F or below comes every winter, usually between December 21 and March 2.

July is the warmest month at Westchester Co Airport, NY, averaging 83°F by day and 65°F at night; January is the coldest at 37°F and 22°F. A freezing night is all but certain in every month from November to April (a 90% chance or more). From May to September the chance of a 32°F night stays under 10% each month.

Warmth for growing adds up to 3,082 growing degree days a year (base 50°F), more than at 82% of the 28 Connecticut stations. 31% of them (964) have built up by the end of June, and July adds the most, 745. Precipitation totals 47.7 inches a year, most in September (4.9") and least in February (2.5"); May to September bring 45% of it.

The nearest other station, Stamford 5 N, CT, 8 miles northeast of Greenwich and 189 feet lower, has a last frost 5 days later (April 17), a first frost 8 days earlier (October 23), a season 12 days shorter.

The first measurable snow (0.1 inch or more) in Greenwich usually arrives around December 8, and the last of the season around March 21. Those are the middle dates across the winters of 1991–2020 at Stamford 5 N, CT, 7.8 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 22 days after the last snow.

ZIP 06830 is 5 miles from Westchester Co Airport, NY, which stands at 379 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 12 other ZIP codes share the station; its figures are presented in full for 10573 (Rye Brook). The 2023 USDA Plant Hardiness Zone Map lists ZIP 06830 in zone 7a, the band where the coldest night of the year averaged 0 to 5°F (-17.8 to -15.0°C) over 1991–2020; a zone describes winter lows, not frost dates.