Frost Dates for 02472 — Watertown, Massachusetts

Half of springs at Jamaica Plain, MA see their last 32°F night by April 19; only one in ten is past it by April 6, and one in ten still has one after May 3. Planting tender crops after April 24 leaves a 30% risk of a frost on them, after April 28 20%, and after May 3 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 23 in half of years, as early as October 8 one year in ten, and holds off past November 5 one year in ten. A hard freeze of 28°F follows 11 days later, around November 3; in spring the one-in-ten date for 28°F is April 21, 12 days before the 32°F one. The freeze-free season lasts 185 days in a typical year, longer than at 79% of the 71 Massachusetts stations; it reaches 204 days one year in ten and falls short of 165 one year in ten. On average 121 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 13 days longer, to about May 2, and return around October 10. Severe cold of 16°F or below comes every winter, usually between December 12 and March 9.

July is the warmest month at Jamaica Plain, MA, averaging 85°F by day and 64°F at night; January is the coldest at 37°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 15% of years.

Warmth for growing adds up to 3,047 growing degree days a year (base 50°F), more than at 90% of the 71 Massachusetts stations. 31% of them (931) have built up by the end of June, and July adds the most, 755. Precipitation totals 49.4 inches a year, most in December (5.1") and least in July (3.5"); May to September bring 38% of it.

The nearest other station, Bedford Hanscom Field, MA, 9 miles northwest of Watertown, has a last frost 9 days later (April 28), a first frost 13 days earlier (October 10), a season 20 days shorter.

The first measurable snow (0.1 inch or more) in Watertown usually arrives around December 2, and the last of the season around March 29. Those are the middle dates across the winters of 1991–2020 at Boston Logan International Airport, MA, 8.8 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 21 days after the last snow.

ZIP 02472 is 6 miles from Jamaica Plain, MA, which stands at 95 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 31 other ZIP codes share the station; its figures are presented in full for 02124 (Dorchester). The 2023 USDA Plant Hardiness Zone Map lists ZIP 02472 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.