Frost Dates for 04730 — Houlton, Maine

Half of springs at Houlton International Airport, ME see their last 32°F night by May 27; only one in ten is past it by May 9, and one in ten still has one after June 10. Planting tender crops after June 2 leaves a 30% risk of a frost on them, after June 5 20%, and after June 10 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 September 18 in half of years, as early as September 5 one year in ten, and holds off past October 2 one year in ten. A hard freeze of 28°F follows 13 days later, around October 1; in spring the one-in-ten date for 28°F is May 28, 13 days before the 32°F one. The freeze-free season lasts 115 days in a typical year, the shortest of the 52 Maine stations; it reaches 135 days one year in ten and falls short of 94 one year in ten. On average 190 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 June 10, and return around September 7. Severe cold of 16°F or below comes every winter, usually between November 9 and April 8.

July is the warmest month at Houlton International Airport, ME, averaging 78°F by day and 54°F at night; January is the coldest at 23°F and 3°F. A freezing night is all but certain in every month from October to May (a 90% chance or more). From July to August the chance of a 32°F night stays under 10% each month. In spring, June still brings one in 35% of years.

Warmth for growing adds up to 1,636 growing degree days a year (base 50°F), fewer than at 96% of the 52 Maine stations. 26% of them (433) have built up by the end of June, and July adds the most, 499. Precipitation totals 39.3 inches a year, most in June (4.0") and least in February (2.0"); May to September bring 46% of it.

The nearest other station, Presque Isle, ME, 37 miles north of Houlton, has a last frost 13 days earlier (May 14), a first frost 8 days later (September 26), a season 16 days longer.

The first measurable snow (0.1 inch or more) in Houlton usually arrives around November 1, and the last of the season around April 16. Those are the middle dates across the winters of 1991–2020 at Houlton 5N, ME, 5.8 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 41 days after the last snow.

ZIP 04730 is 4 miles from Houlton International Airport, ME, which stands at 476 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. The 2023 USDA Plant Hardiness Zone Map lists ZIP 04730 in zone 4b, the band where the coldest night of the year averaged -25 to -20°F (-31.7 to -28.9°C) over 1991–2020; a zone describes winter lows, not frost dates.