Kennewick, WA 99338 Frost Dates
99338, near Kennewick, WA: the frost window
The last spring frost here typically falls around 03/28, about 212 days from today. Fall's first freeze usually shows up around 10/30, roughly 216 days after the last spring frost.
Zone 7b (5 to 10°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 Kennewick, not a forecast for this year.
Stretching the season past the first frost
Kennewick's growing season runs out in roughly 9 weeks — a cold frame or greenhouse kit is the usual way to keep cool-weather crops going past the first frost.
Why 03/28 isn't a guarantee
03/28 is the middle of 30 years of NOAA records, not a promise. Getting tender plants in by 03/09 carries real risk, frost has hit that late in about 9 of 10 years here. Wait until 04/10 and only about 1 year in 10 sees frost after that.
Kennewick against the rest of the dataset
At roughly 216 frost-free days, Kennewick places 13,704 of 40,283 ZIP codes in this dataset. Within WA, it ranks 253 of 700.
Learn more
Two guides worth reading on 99338: the frost range, on how to read the range around Kennewick's dates instead of trusting one, and local microclimates, on what one yard in Kennewick can differ from the 99338 normal.