Rockville, MD 20851 Frost Dates
Frost dates for Rockville, MD, ZIP 20851
Around 04/01 is the usual last spring frost, about 216 days away. The first fall frost typically arrives around 11/06, about 219 frost-free days later.
The USDA Plant Hardiness Zone Map puts Rockville in Zone 7b (5 to 10°F average annual minimum); frost dates are NOAA's 1991-2020 station normal, not this year's forecast.
What to do before the first frost
Zone 7b around Rockville 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.
The actual range around Rockville's last frost
04/01 is the middle of 30 years of NOAA records, not a promise. Plant by 03/19 and you're betting against frost in roughly 9 years out of 10. 04/15 is the safer bet, historically only a 1-in-10 chance of frost that late.
How Rockville compares
At roughly 219 frost-free days, Rockville places 12,953 of 40,283 ZIP codes in this dataset. Within MD, it ranks 226 of 583.
Learn more
zone vs. frost date explains why Zone 7b and Rockville's frost date answer different questions, and the frost range explains how to read the range around Rockville's dates instead of trusting one.