Frost Dates for 06351 — Lisbon, Connecticut

Half of springs at Norwich Public Utility Plt, CT see their last 32°F night by April 14; only one in ten is past it by April 1, and one in ten still has one after April 30. Planting tender crops after April 21 leaves a 30% risk of a frost on them, after April 24 20%, and after April 30 10%. The 16 days between the even-odds date and the one-in-ten date is wider than at 82% of the 28 Connecticut stations behind this site's ZIP pages.

In fall the first 32°F night comes by October 24 in half of years, as early as October 9 one year in ten, and holds off past November 7 one year in ten. A hard freeze of 28°F follows 12 days later, around November 5; in spring the one-in-ten date for 28°F is April 16, 14 days before the 32°F one. The freeze-free season lasts 192 days in a typical year, longer than at 75% of the 28 Connecticut stations; it reaches 211 days one year in ten and falls short of 170 one year in ten. On average 124 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 16 days longer, to about April 30, and return around October 12. Severe cold of 16°F or below comes every winter, usually between December 16 and March 4.

July is the warmest month at Norwich Public Utility Plt, CT, averaging 84°F by day and 65°F at night; January is the coldest at 38°F and 21°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 3,066 growing degree days a year (base 50°F), more than at 71% of the 28 Connecticut stations. 31% of them (945) have built up by the end of June, and July adds the most, 758. Precipitation totals 52.3 inches a year, most in March (5.1") and least in May (3.6"); May to September bring 40% of it.

The nearest other station, Hampton, CT, 12 miles north of Lisbon and 470 feet higher, has a last frost 16 days later (April 30), a first frost 9 days earlier (October 15), a season 25 days shorter.

The first measurable snow (0.1 inch or more) in Lisbon 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, 7.1 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 30 days after the last snow.

ZIP 06351 is 7 miles from Norwich Public Utility Plt, CT, which stands at 20 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 06360 (Norwich). The 2023 USDA Plant Hardiness Zone Map lists ZIP 06351 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.