Frost Dates for 04011 — Brunswick, Maine

Half of springs at Brunswick NAS, ME see their last 32°F night by May 2; only one in ten is past it by April 24, and one in ten still has one after May 14. Planting tender crops after May 6 leaves a 30% risk of a frost on them, after May 9 20%, and after May 14 10%. The 12 days between the even-odds date and the one-in-ten date is narrower than at 67% of the 52 Maine stations behind this site's ZIP pages.

In fall the first 32°F night comes by October 10 in half of years, as early as September 29 one year in ten, and holds off past October 27 one year in ten. A hard freeze of 28°F follows 13 days later, around October 23; in spring the one-in-ten date for 28°F is May 1, 13 days before the 32°F one. The freeze-free season lasts 160 days in a typical year, longer than at 71% of the 52 Maine stations; it reaches 177 days one year in ten and falls short of 143 one year in ten. On average 151 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 13, and return around October 1. Severe cold of 16°F or below comes every winter, usually between November 27 and March 18.

July is the warmest month at Brunswick NAS, ME, averaging 79°F by day and 59°F at night; January is the coldest at 30°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 August the chance of a 32°F night stays under 10% each month. In spring, May still brings one in 57% of years.

Warmth for growing adds up to 2,120 growing degree days a year (base 50°F), more than at 63% of the 52 Maine stations. 27% of them (566) have built up by the end of June, and July adds the most, 600. Precipitation totals 50.2 inches a year, most in October (6.0") and least in August (3.3"); May to September bring 38% of it.

The nearest other station, Bath, ME, 6 miles northeast of Brunswick, has a last frost 8 days later (May 10), a first frost 4 days earlier (October 6), a season 11 days shorter.

The first measurable snow (0.1 inch or more) in Brunswick usually arrives around November 24, and the last of the season around April 8. Those are the middle dates across the winters of 1991–2020 at Bath, ME, 5.6 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 24 days after the last snow.

ZIP 04011 is 1 mile from Brunswick NAS, ME, which stands at 70 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 2 other ZIP codes share the station. The 2023 USDA Plant Hardiness Zone Map lists ZIP 04011 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.