Frost Dates for 04348 — Jefferson, Maine

Half of springs at Newcastle, ME see their last 32°F night by April 27; only one in ten is past it by April 16, and one in ten still has one after May 10. Planting tender crops after May 2 leaves a 30% risk of a frost on them, after May 5 20%, and after May 10 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 18 in half of years, as early as October 3 one year in ten, and holds off past November 2 one year in ten. A hard freeze of 28°F follows 14 days later, around November 1; in spring the one-in-ten date for 28°F is April 27, 13 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 191 days one year in ten and falls short of 154 one year in ten. On average 142 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 9, and return around October 5. Severe cold of 16°F or below comes every winter, usually between December 1 and March 19.

July is the warmest month at Newcastle, ME, averaging 78°F by day and 60°F at night; January is the coldest at 30°F and 15°F. A freezing night is all but certain in every month from November 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 37% of years.

Warmth for growing adds up to 2,166 growing degree days a year (base 50°F), more than at 73% of the 52 Maine stations. 28% of them (602) have built up by the end of June, and July adds the most, 591. Precipitation totals 49.3 inches a year, most in October (5.0") and least in July (3.4"); May to September bring 39% of it.

The nearest other station, Gardiner, ME, 14 miles west of Jefferson, has a last frost 4 days later (May 1), a first frost 7 days earlier (October 11), a season 9 days shorter.

The first measurable snow (0.1 inch or more) in Jefferson usually arrives around November 19, and the last of the season around April 13. Those are the middle dates across the winters of 1991–2020 at Newcastle, ME, 11.9 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 14 days after the last snow.

ZIP 04348 is 12 miles from Newcastle, ME, which stands at 213 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 2 other ZIP codes share the station; its figures are presented in full for 04572 (Waldoboro). The 2023 USDA Plant Hardiness Zone Map lists ZIP 04348 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.