Frost Dates for 03901 — Berwick, Maine

Half of springs at Rochester Skyhaven Airport, NH see their last 32°F night by April 30; only one in ten is past it by April 18, and one in ten still has one after May 13. Planting tender crops after May 5 leaves a 30% risk of a frost on them, after May 8 20%, and after May 13 10%. The 13 days between the even-odds date and the one-in-ten date is narrower than at 33% of the 52 Maine stations behind this site's ZIP pages.

In fall the first 32°F night comes by October 9 in half of years, as early as September 27 one year in ten, and holds off past October 25 one year in ten. A hard freeze of 28°F follows 14 days later, around October 23; in spring the one-in-ten date for 28°F is April 29, 14 days before the 32°F one. The freeze-free season lasts 161 days in a typical year, longer than at 73% of the 52 Maine stations; it reaches 181 days one year in ten and falls short of 142 one year in ten. On average 145 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 12 days longer, to about May 12, and return around September 30. Severe cold of 16°F or below comes every winter, usually between December 1 and March 18.

July is the warmest month at Rochester Skyhaven Airport, NH, averaging 82°F by day and 60°F at night; January is the coldest at 33°F and 15°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 48% of years.

Warmth for growing adds up to 2,438 growing degree days a year (base 50°F), the most of the 52 Maine stations. 30% of them (743) have built up by the end of June, and July adds the most, 643. Precipitation totals 41.2 inches a year, most in October (4.4") and least in February (2.2"); May to September bring 42% of it.

The nearest other station, Durham 2 N, NH, 9 miles southwest of Berwick and 204 feet lower, has a last frost 3 days later (May 3), a first frost 1 day later (October 10), a season 3 days shorter.

The first measurable snow (0.1 inch or more) in Berwick usually arrives around December 2, and the last of the season around March 31. Those are the middle dates across the winters of 1991–2020 at Rochester, NH, 6.9 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 30 days after the last snow.

ZIP 03901 is 4 miles from Rochester Skyhaven Airport, NH, which stands at 323 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 10 other ZIP codes share the station; its figures are presented in full for 03867 (Rochester). The 2023 USDA Plant Hardiness Zone Map lists ZIP 03901 in zone 6a, the band where the coldest night of the year averaged -10 to -5°F (-23.3 to -20.6°C) over 1991–2020; a zone describes winter lows, not frost dates.