Mount Vernon, WA 98273 Frost Dates
98273, near Mount Vernon, WA: the frost window
Around 03/27 is the usual last spring frost, about 211 days away. Fall's first freeze usually shows up around 11/06, roughly 224 days after the last spring frost.
The USDA Plant Hardiness Zone Map puts Mount Vernon in Zone 8b (15 to 20°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
Mount Vernon'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.
Why 03/27 isn't a guarantee
03/27 is the middle of 30 years of NOAA records, not a promise. Getting tender plants in by 03/08 carries real risk, frost has hit that late in about 9 of 10 years here. Wait until 04/17 and only about 1 year in 10 sees frost after that.
Mount Vernon against the rest of the dataset
At roughly 224 frost-free days, Mount Vernon places 11,745 of 40,283 ZIP codes in this dataset. Within WA, it ranks 210 of 700.
Learn more
Two guides worth reading on 98273: local microclimates, on what one yard in Mount Vernon can differ from the 98273 normal, and zone vs. frost date, on why Zone 8b and Mount Vernon's frost date answer different questions.