Williamsport, MD 21781 Frost Dates
21781, near Williamsport, MD: the frost window
Typically, the last spring freeze lands around 04/11, roughly 226 days out. Fall's first freeze usually shows up around 10/28, roughly 199 days after the last spring frost.
Williamsport sits in USDA Zone 7a (0 to 5°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.
Stretching the season past the first frost
Williamsport's growing season runs out in roughly 9 weeks — a cold frame or greenhouse kit is the usual way to keep cool-weather crops going past the first frost.
Why 04/11 isn't a guarantee
04/11 is the middle of 30 years of NOAA records, not a promise. Getting tender plants in by 03/29 carries real risk, frost has hit that late in about 9 of 10 years here. Wait until 04/27 and only about 1 year in 10 sees frost after that.
Williamsport against the rest of the dataset
About 199 days separate Williamsport's last and first frost, putting it 18,136 of 40,283 ZIP codes nationally. Within MD, it ranks 473 of 583.
Learn more
Two guides worth reading on 21781: local microclimates, on what one yard in Williamsport can differ from the 21781 normal, and zone vs. frost date, on why Zone 7a and Williamsport's frost date answer different questions.