Washington, DC 20340 Frost Dates
Frost dates for Washington, DC, ZIP 20340
Around 03/29 is the usual last spring frost, about 213 days away. The first fall frost typically arrives around 11/08, about 224 frost-free days later.
Zone 8a (10 to 15°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 Washington, not a forecast for this year.
What to do before the first frost
Zone 8a around Washington has about 10 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 03/29 isn't a guarantee
03/29 is the middle of 30 years of NOAA records, not a promise. Plant by 03/15 and you're betting against frost in roughly 9 years out of 10. 04/11 is the safer bet, historically only a 1-in-10 chance of frost that late.
How Washington compares
At roughly 224 frost-free days, Washington places 11,620 of 40,283 ZIP codes in this dataset. Within DC, it ranks 148 of 246.
Learn more
local microclimates explains what one yard in Washington can differ from the 20340 normal, and zone vs. frost date explains why Zone 8a and Washington's frost date answer different questions.