Frost Dates for 02452 — Waltham, Massachusetts

Half of springs at Bedford Hanscom Field, MA see their last 32°F night by April 28; only one in ten is past it by April 13, and one in ten still has one after May 12. Planting tender crops after May 3 leaves a 30% risk of a frost on them, after May 7 20%, and after May 12 10%. The 14 days between the even-odds date and the one-in-ten date is wider than at 51% of the 71 Massachusetts stations behind this site's ZIP pages.

In fall the first 32°F night comes by October 10 in half of years, as early as September 28 one year in ten, and holds off past October 28 one year in ten. A hard freeze of 28°F follows 15 days later, around October 25; in spring the one-in-ten date for 28°F is April 29, 13 days before the 32°F one. The freeze-free season lasts 165 days in a typical year, shorter than at 58% of the 71 Massachusetts stations; it reaches 186 days one year in ten and falls short of 146 one year in ten. On average 139 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 10, and return around October 1. Severe cold of 16°F or below comes every winter, usually between December 4 and March 13.

July is the warmest month at Bedford Hanscom Field, MA, averaging 85°F by day and 62°F at night; January is the coldest at 37°F and 18°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 40% of years.

Warmth for growing adds up to 2,906 growing degree days a year (base 50°F), more than at 80% of the 71 Massachusetts stations. 31% of them (909) have built up by the end of June, and July adds the most, 730. Precipitation totals 42.6 inches a year, most in October (4.2") and least in February (2.7"); May to September bring 41% of it.

The nearest other station, Bedford, MA, 7 miles northwest of Waltham, has a last frost 1 day earlier (April 27), a first frost 3 days later (October 13), a season 4 days longer.

The first measurable snow (0.1 inch or more) in Waltham usually arrives around November 23, and the last of the season around April 1. Those are the middle dates across the winters of 1991–2020 at Bedford, MA, 7 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 27 days after the last snow.

ZIP 02452 is 6 miles from Bedford Hanscom Field, MA, which stands at 133 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 5 other ZIP codes share the station; its figures are presented in full for 02451 (Waltham). The 2023 USDA Plant Hardiness Zone Map lists ZIP 02452 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.