Washington, DC 20451 Frost Dates
20451, near Washington, DC: the frost window
Typically, the last spring freeze lands around 03/24, roughly 208 days out. Fall's first freeze usually shows up around 11/18, roughly 241 days after the last spring frost.
Washington sits in USDA Zone 8a (10 to 15°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
Washington's growing season runs out in roughly 12 weeks — a cold frame or greenhouse kit is the usual way to keep cool-weather crops going past the first frost.
Why 03/24 isn't a guarantee
03/24 is the middle of 30 years of NOAA records, not a promise. Getting tender plants in by 03/07 carries real risk, frost has hit that late in about 9 of 10 years here. Wait until 04/06 and only about 1 year in 10 sees frost after that.
Washington against the rest of the dataset
At roughly 241 frost-free days, Washington places 8,445 of 40,283 ZIP codes in this dataset. Within DC, it ranks 26 of 246.
Learn more
Two guides worth reading on 20451: zone vs. frost date, on why Zone 8a and Washington's frost date answer different questions, and the frost range, on how to read the range around Washington's dates instead of trusting one.