Gaithersburg, MD 20915 Frost Dates
20915, near Gaithersburg, MD: the frost window
Typically, the last spring freeze lands around 04/01, roughly 216 days out. Fall's first freeze usually shows up around 11/06, roughly 219 days after the last spring frost.
Zone 7b (5 to 10°F average annual minimum) comes from the USDA Plant Hardiness Zone Map; the frost dates above are the 1991-2020 normal at the nearest reporting NOAA station for Gaithersburg, not a forecast for this year.
Stretching the season past the first frost
Gaithersburg's growing season runs out in roughly 10 weeks — a cold frame or greenhouse kit is the usual way to keep cool-weather crops going past the first frost.
How much risk comes with planting early here
04/01 is the middle of 30 years of NOAA records, not a promise. Getting tender plants in by 03/19 carries real risk, frost has hit that late in about 9 of 10 years here. Wait until 04/15 and only about 1 year in 10 sees frost after that.
Gaithersburg against the rest of the dataset
Gaithersburg's growing season runs about 219 days, ranking 12,948 of 40,283 US ZIP codes measured here, longest to shortest. Within MD, it ranks 221 of 583.
Learn more
Two guides worth reading on 20915: the frost range, on how to read the range around Gaithersburg's dates instead of trusting one, and local microclimates, on what one yard in Gaithersburg can differ from the 20915 normal.