Watertown, MA 02478 Frost Dates
Frost dates for Watertown, MA, ZIP 02478
The last spring frost here typically falls around 04/19, about 234 days from today. The first fall frost typically arrives around 10/23, about 185 frost-free days later.
Watertown sits in USDA Zone 6b (-5 to 0°F average annual minimum). The dates above are NOAA's 1991-2020 normal at the nearest reporting station, a 30-year average, not a forecast.
What to do before the first frost
Zone 6b around Watertown has about 8 weeks left before the first fall frost — that's the usual window to get a cold frame up if you want to keep harvesting past it.
Why 04/19 isn't a guarantee
04/19 is the middle of 30 years of NOAA records, not a promise. Plant by 04/06 and you're betting against frost in roughly 9 years out of 10. 05/03 is the safer bet, historically only a 1-in-10 chance of frost that late.
How Watertown compares
Watertown's growing season runs about 185 days, ranking 23,065 of 40,283 US ZIP codes measured here, longest to shortest. Within MA, it ranks 196 of 712.
Learn more
zone vs. frost date explains why Zone 6b and Watertown's frost date answer different questions, and the frost range explains how to read the range around Watertown's dates instead of trusting one.