Mattawa, WA 99349 Frost Dates
99349, near Mattawa, WA: the frost window
Typically, the last spring freeze lands around 03/24, roughly 208 days out. Fall's first freeze usually shows up around 11/04, roughly 222 days after the last spring frost.
Mattawa sits in USDA Zone 7a (0 to 5°F average annual minimum). The dates above are NOAA's 1991-2020 normal at the nearest reporting station, a 30-year average, not a forecast.
Stretching the season past the first frost
Mattawa'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.
How much risk comes with planting early here
03/24 is the middle of 30 years of NOAA records, not a promise. Getting tender plants in by 03/04 carries real risk, frost has hit that late in about 9 of 10 years here. Wait until 04/07 and only about 1 year in 10 sees frost after that.
Mattawa against the rest of the dataset
At roughly 222 frost-free days, Mattawa places 12,260 of 40,283 ZIP codes in this dataset. Within WA, it ranks 237 of 700.
Learn more
Two guides worth reading on 99349: zone vs. frost date, on why Zone 7a and Mattawa's frost date answer different questions, and the frost range, on how to read the range around Mattawa's dates instead of trusting one.