Frost Dates for 02777 — Swansea, Massachusetts

Half of springs at Tiverton, RI see their last 32°F night by April 11; only one in ten is past it by April 1, and one in ten still has one after April 22. Planting tender crops after April 16 leaves a 30% risk of a frost on them, after April 19 20%, and after April 22 10%. The 11 days between the even-odds date and the one-in-ten date is narrower than at 96% of the 71 Massachusetts stations behind this site's ZIP pages.

In fall the first 32°F night comes by November 2 in half of years, as early as October 20 one year in ten, and holds off past November 15 one year in ten. A hard freeze of 28°F follows 11 days later, around November 13; in spring the one-in-ten date for 28°F is April 11, 11 days before the 32°F one. The freeze-free season lasts 203 days in a typical year, longer than at 92% of the 71 Massachusetts stations; it reaches 220 days one year in ten and falls short of 186 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 15 days longer, to about April 26, and return around October 21. Severe cold of 16°F or below comes every winter, usually between December 23 and March 3.

July is the warmest month at Tiverton, RI, averaging 85°F by day and 65°F at night; January is the coldest at 39°F and 24°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 90% of years.

Warmth for growing adds up to 3,226 growing degree days a year (base 50°F), more than at 99% of the 71 Massachusetts stations. 29% of them (951) have built up by the end of June, and July adds the most, 773. Precipitation totals 49.4 inches a year, most in March (5.6") and least in July (3.0"); May to September bring 36% of it.

The nearest other station, Providence T F Green Airport, RI, 11 miles west of Swansea, has the same 50% last-frost date, a first frost 3 days earlier (October 30), a season 4 days shorter.

The first measurable snow (0.1 inch or more) in Swansea 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 Tiverton, RI, 7.9 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 21 days after the last snow.

ZIP 02777 is 8 miles from Tiverton, RI, which stands at 90 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 11 other ZIP codes share the station; its figures are presented in full for 02720 (Fall River). The 2023 USDA Plant Hardiness Zone Map lists ZIP 02777 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.