Frost Dates for 04363 — Windsor, Maine

Half of springs at Augusta State Airport, ME see their last 32°F night by April 27; only one in ten is past it by April 15, and one in ten still has one after May 7. Planting tender crops after May 1 leaves a 30% risk of a frost on them, after May 3 20%, and after May 7 10%. The 10 days between the even-odds date and the one-in-ten date is the narrowest of the 52 Maine stations behind this site's ZIP pages, so the end of frost is fairly predictable.

In fall the first 32°F night comes by October 16 in half of years, as early as October 2 one year in ten, and holds off past October 31 one year in ten. A hard freeze of 28°F follows 15 days later, around October 31; in spring the one-in-ten date for 28°F is April 26, 11 days before the 32°F one. The freeze-free season lasts 172 days in a typical year, longer than at 85% of the 52 Maine stations; it reaches 192 days one year in ten and falls short of 154 one year in ten. On average 147 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 8, and return around October 4. Severe cold of 16°F or below comes every winter, usually between December 1 and March 19.

July is the warmest month at Augusta State Airport, ME, averaging 80°F by day and 60°F at night; January is the coldest at 29°F and 12°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 30% of years.

Warmth for growing adds up to 2,282 growing degree days a year (base 50°F), more than at 87% of the 52 Maine stations. 28% of them (650) have built up by the end of June, and July adds the most, 623. Precipitation totals 41.8 inches a year, most in October (4.7") and least in February (2.3"); May to September bring 43% of it.

The nearest other station, Gardiner, ME, 12 miles southwest of Windsor and 217 feet lower, has a last frost 4 days later (May 1), a first frost 5 days earlier (October 11), a season 9 days shorter.

The first measurable snow (0.1 inch or more) in Windsor usually arrives around November 24, and the last of the season around April 5. Those are the middle dates across the winters of 1991–2020 at Gardiner, ME, 12 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 04363 is 11 miles from Augusta State Airport, ME, which stands at 350 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 04330 (Augusta). The 2023 USDA Plant Hardiness Zone Map lists ZIP 04363 in zone 5b, the band where the coldest night of the year averaged -15 to -10°F (-26.1 to -23.3°C) over 1991–2020; a zone describes winter lows, not frost dates.