Grand Coulee, WA 99133 Frost Dates
99133, near Grand Coulee, WA: the frost window
The last spring frost here typically falls around 04/22, about 237 days from today. Fall's first freeze usually shows up around 10/21, roughly 180 days after the last spring frost.
Grand Coulee 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
Grand Coulee's growing season runs out in roughly 8 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
04/22 is the middle of 30 years of NOAA records, not a promise. Getting tender plants in by 04/05 carries real risk, frost has hit that late in about 9 of 10 years here. Wait until 05/07 and only about 1 year in 10 sees frost after that.
Grand Coulee against the rest of the dataset
At roughly 180 frost-free days, Grand Coulee places 24,963 of 40,283 ZIP codes in this dataset. Within WA, it ranks 440 of 700.
Learn more
Two guides worth reading on 99133: zone vs. frost date, on why Zone 7a and Grand Coulee's frost date answer different questions, and the frost range, on how to read the range around Grand Coulee's dates instead of trusting one.