Frost Dates for 05488 — Swanton, Vermont

Half of springs at St Albans Radio, VT see their last 32°F night by May 1; only one in ten is past it by April 20, and one in ten still has one after May 16. Planting tender crops after May 7 leaves a 30% risk of a frost on them, after May 10 20%, and after May 16 10%. The 15 days between the even-odds date and the one-in-ten date is narrower than at 24% of the 41 Vermont stations behind this site's ZIP pages.

In fall the first 32°F night comes by October 12 in half of years, as early as September 28 one year in ten, and holds off past October 26 one year in ten. A hard freeze of 28°F follows 11 days later, around October 23; in spring the one-in-ten date for 28°F is May 5, 11 days before the 32°F one. The freeze-free season lasts 161 days in a typical year, longer than at 83% of the 41 Vermont stations; it reaches 181 days one year in ten and falls short of 142 one year in ten. On average 148 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 12, and return around October 2. Severe cold of 16°F or below comes every winter, usually between November 24 and March 30.

July is the warmest month at St Albans Radio, VT, averaging 79°F by day and 61°F at night; January is the coldest at 25°F and 8°F. A freezing night is all but certain in every month from October to April (a 90% chance or more). From June to August the chance of a 32°F night stays under 10% each month. In spring, May still brings one in 53% of years.

Warmth for growing adds up to 2,304 growing degree days a year (base 50°F), more than at 68% of the 41 Vermont stations. 31% of them (710) have built up by the end of June, and July adds the most, 625. Precipitation totals 38.2 inches a year, most in June (4.1") and least in February (1.9"); May to September bring 50% of it.

The nearest other station, Chazy, NY, 14 miles west of Swanton and 223 feet lower, has a last frost 1 day earlier (April 30), the same first-frost date, a season 3 days longer.

The first measurable snow (0.1 inch or more) in Swanton usually arrives around October 31, and the last of the season around April 14. Those are the middle dates across the winters of 1991–2020 at St Albans Radio, VT, 5.1 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 17 days after the last snow.

ZIP 05488 is 5 miles from St Albans Radio, VT, which stands at 380 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 3 other ZIP codes share the station; its figures are presented in full for 05478 (Saint Albans). The 2023 USDA Plant Hardiness Zone Map lists ZIP 05488 in zone 5a, the band where the coldest night of the year averaged -20 to -15°F (-28.9 to -26.1°C) over 1991–2020; a zone describes winter lows, not frost dates.