Frost Dates for 04915 — Belfast, Maine

Half of springs at Belfast, ME see their last 32°F night by May 7; only one in ten is past it by April 28, and one in ten still has one after May 21. Planting tender crops after May 13 leaves a 30% risk of a frost on them, after May 16 20%, and after May 21 10%. The 14 days between the even-odds date and the one-in-ten date is wider than at 69% of the 52 Maine stations behind this site's ZIP pages.

In fall the first 32°F night comes by October 5 in half of years, as early as September 24 one year in ten, and holds off past October 20 one year in ten. A hard freeze of 28°F follows 14 days later, around October 19; in spring the one-in-ten date for 28°F is May 6, 15 days before the 32°F one. The freeze-free season lasts 151 days in a typical year, shorter than at 48% of the 52 Maine stations; it reaches 167 days one year in ten and falls short of 133 one year in ten. On average 162 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 14 days longer, to about May 21, and return around September 27. Severe cold of 16°F or below comes every winter, usually between November 25 and March 25.

July is the warmest month at Belfast, ME, averaging 77°F by day and 57°F at night; January is the coldest at 30°F and 10°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 80% of years.

Warmth for growing adds up to 1,802 growing degree days a year (base 50°F), fewer than at 87% of the 52 Maine stations. 25% of them (456) have built up by the end of June, and July adds the most, 521. Precipitation totals 49.0 inches a year, most in October (5.4") and least in August (3.1"); May to September bring 38% of it.

The nearest other station, W Rockport 1 NNW, ME, 19 miles south of Belfast and 341 feet higher, has a last frost 10 days earlier (April 27), a first frost 14 days later (October 19), a season 24 days longer.

The first measurable snow (0.1 inch or more) in Belfast 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 Belfast, ME, 3.8 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 37 days after the last snow.

ZIP 04915 is 4 miles from Belfast, ME, which stands at 20 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 4 other ZIP codes share the station. The 2023 USDA Plant Hardiness Zone Map lists ZIP 04915 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.