Seattle, WA 98109 Frost Dates
Seattle, WA: when does the frost end?
Around 03/08 is the usual last spring frost, about 192 days away. Fall's first freeze usually shows up around 11/23, roughly 259 days after the last spring frost.
The USDA Plant Hardiness Zone Map puts Seattle in Zone 9a (20 to 25°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
With roughly 12 weeks until Seattle's first fall frost, a row cover or cold frame is what stretches the last few weeks of harvest here.
The actual range around Seattle's last frost
03/08 is the middle of 30 years of NOAA records, not a promise. Getting tender plants in by 02/13 carries real risk, frost has hit that late in about 9 of 10 years here. Wait until 03/29 and only about 1 year in 10 sees frost after that.
Seattle against the rest of the dataset
At roughly 259 frost-free days, Seattle places 6,509 of 40,283 ZIP codes in this dataset. Within WA, it ranks 25 of 700.
Learn more
Before leaning on 98109's figures: the frost range explains how to read the range around Seattle's dates instead of trusting one, while local microclimates explains what one yard in Seattle can differ from the 98109 normal.