Frost Dates for 01887 — Wilmington, Massachusetts

Half of springs at Reading, MA see their last 32°F night by April 25; only one in ten is past it by April 13, and one in ten still has one after May 8. Planting tender crops after May 1 leaves a 30% risk of a frost on them, after May 4 20%, and after May 8 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 October 17 in half of years, as early as October 3 one year in ten, and holds off past November 1 one year in ten. A hard freeze of 28°F follows 13 days later, around October 30; in spring the one-in-ten date for 28°F is April 24, 14 days before the 32°F one. The freeze-free season lasts 174 days in a typical year, longer than at 58% of the 71 Massachusetts stations; it reaches 193 days one year in ten and falls short of 156 one year in ten. On average 134 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 7, and return around October 6. Severe cold of 16°F or below comes every winter, usually between December 4 and March 12.

July is the warmest month at Reading, MA, averaging 84°F by day and 63°F at night; January is the coldest at 38°F and 19°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 30% of years.

Warmth for growing adds up to 2,875 growing degree days a year (base 50°F), more than at 77% of the 71 Massachusetts stations. 31% of them (882) have built up by the end of June, and July adds the most, 721. Precipitation totals 49.9 inches a year, most in December (5.0") and least in August (3.5"); May to September bring 39% of it.

The nearest other station, Bedford, MA, 8 miles southwest of Wilmington, has a last frost 2 days later (April 27), a first frost 4 days earlier (October 13), a season 5 days shorter.

The first measurable snow (0.1 inch or more) in Wilmington usually arrives around November 24, and the last of the season around April 2. Those are the middle dates across the winters of 1991–2020 at Reading, MA, 3.3 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 23 days after the last snow.

ZIP 01887 is 3 miles from Reading, MA, which stands at 110 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 9 other ZIP codes share the station; its figures are presented in full for 01801 (Woburn). The 2023 USDA Plant Hardiness Zone Map lists ZIP 01887 in zone 6b, the band where the coldest night of the year averaged -5 to 0°F (-20.6 to -17.8°C) over 1991–2020; a zone describes winter lows, not frost dates.