Frost Dates for 06249 — Lebanon, Connecticut

Half of springs at Willimantic Windham Airport, CT see their last 32°F night by April 28; only one in ten is past it by April 17, and one in ten still has one after May 11. Planting tender crops after May 3 leaves a 30% risk of a frost on them, after May 7 20%, and after May 11 10%. The 13 days between the even-odds date and the one-in-ten date is narrower than at 86% of the 28 Connecticut stations behind this site's ZIP pages.

In fall the first 32°F night comes by October 13 in half of years, as early as October 2 one year in ten, and holds off past October 29 one year in ten. A hard freeze of 28°F follows 12 days later, around October 25; in spring the one-in-ten date for 28°F is April 29, 12 days before the 32°F one. The freeze-free season lasts 167 days in a typical year, shorter than at 75% of the 28 Connecticut stations; it reaches 189 days one year in ten and falls short of 149 one year in ten. On average 135 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 11 days longer, to about May 9, and return around October 3. Severe cold of 16°F or below comes every winter, usually between December 1 and March 13.

July is the warmest month at Willimantic Windham Airport, CT, averaging 83°F by day and 62°F at night; January is the coldest at 36°F and 18°F. A freezing night is all but certain in every month from October to April (a 90% chance or more). From June to September the chance of a 32°F night stays under 10% each month. In spring, May still brings one in 38% of years.

Warmth for growing adds up to 2,758 growing degree days a year (base 50°F), fewer than at 57% of the 28 Connecticut stations. 31% of them (865) have built up by the end of June, and July adds the most, 693. Precipitation totals 43.5 inches a year, most in August (4.4") and least in February (2.7"); May to September bring 43% of it.

The nearest other station, Norwich Public Utility Plt, CT, 11 miles southeast of Lebanon and 227 feet lower, has a last frost 14 days earlier (April 14), a first frost 11 days later (October 24), a season 25 days longer.

The first measurable snow (0.1 inch or more) in Lebanon usually arrives around December 10, and the last of the season around March 15. Those are the middle dates across the winters of 1991–2020 at Norwich Public Utility Plt, CT, 11.1 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 44 days after the last snow.

ZIP 06249 is 9 miles from Willimantic Windham Airport, CT, which stands at 247 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 5 other ZIP codes share the station; its figures are presented in full for 06226 (Willimantic). The 2023 USDA Plant Hardiness Zone Map lists ZIP 06249 in zone 6b, the band where the coldest night of the year averaged -5 to 0°F (-20.6 to -17.8°C) over 1991–2020; a zone describes winter lows, not frost dates.