Thurmont, MD 21778 Frost Dates
21778, near Thurmont, MD: the frost window
Around 04/22 is the usual last spring frost, about 237 days away. Fall's first freeze usually shows up around 10/20, roughly 179 days after the last spring frost.
The USDA Plant Hardiness Zone Map puts Thurmont in Zone 7a (0 to 5°F average annual minimum); frost dates are NOAA's 1991-2020 station normal, not this year's forecast.
Stretching the season past the first frost
Thurmont's growing season runs out in roughly 8 weeks — a cold frame or greenhouse kit is the usual way to keep cool-weather crops going past the first frost.
Why 04/22 isn't a guarantee
04/22 is the middle of 30 years of NOAA records, not a promise. Getting tender plants in by 04/07 carries real risk, frost has hit that late in about 9 of 10 years here. Wait until 05/09 and only about 1 year in 10 sees frost after that.
Thurmont against the rest of the dataset
Thurmont's growing season runs about 179 days, ranking 25,274 of 40,283 US ZIP codes measured here, longest to shortest. Within MD, it ranks 547 of 583.
Learn more
Two guides worth reading on 21778: local microclimates, on what one yard in Thurmont can differ from the 21778 normal, and zone vs. frost date, on why Zone 7a and Thurmont's frost date answer different questions.