Frost Dates for 02645 — Harwich, Massachusetts

Half of springs at Chatham Municipal Airport, MA see their last 32°F night by April 13; only one in ten is past it by April 1, and one in ten still has one after April 26. Planting tender crops after April 18 leaves a 30% risk of a frost on them, after April 21 20%, and after April 26 10%. The 13 days between the even-odds date and the one-in-ten date is narrower than at 51% of the 71 Massachusetts stations behind this site's ZIP pages.

In fall the first 32°F night comes by November 4 in half of years, as early as October 21 one year in ten, and holds off past November 18 one year in ten. A hard freeze of 28°F follows 15 days later, around November 19; in spring the one-in-ten date for 28°F is April 11, 15 days before the 32°F one. The freeze-free season lasts 206 days in a typical year, longer than at 94% of the 71 Massachusetts stations; it reaches 224 days one year in ten and falls short of 186 one year in ten. On average 92 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 April 27, and return around October 23. Severe cold of 16°F or below comes every winter, usually between December 31 and February 24.

July is the warmest month at Chatham Municipal Airport, MA, averaging 79°F by day and 64°F at night; January is the coldest at 39°F and 26°F. A freezing night is all but certain in every month from November to April (a 90% chance or more). From May to September the chance of a 32°F night stays under 10% each month.

Warmth for growing adds up to 2,567 growing degree days a year (base 50°F), fewer than at 63% of the 71 Massachusetts stations. 24% of them (628) have built up by the end of June, and July adds the most, 665. Precipitation totals 45.2 inches a year, most in December (5.0") and least in July (2.8"); May to September bring 35% of it.

The nearest other station, W Harwich, MA, 4 miles southwest of Harwich, has the same 50% last-frost date, a first frost 1 day earlier (November 3), a season 2 days shorter.

The first measurable snow (0.1 inch or more) in Harwich usually arrives around December 16, and the last of the season around March 19. Those are the middle dates across the winters of 1991–2020 at Chatham, MA, 6.1 miles away: half of years saw snow earlier, half later. Snow fell in 97% of those winters. The last 32°F night of spring typically comes 25 days after the last snow.

ZIP 02645 is 4 miles from Chatham Municipal Airport, MA, which stands at 68 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 5 other ZIP codes share the station. The 2023 USDA Plant Hardiness Zone Map lists ZIP 02645 in zone 7b, the band where the coldest night of the year averaged 5 to 10°F (-15.0 to -12.2°C) over 1991–2020; a zone describes winter lows, not frost dates.