Winthrop, WA 98833 Frost Dates
Frost dates for Winthrop, WA, ZIP 98833
Typically, the last spring freeze lands around 05/09, roughly 254 days out. The first fall frost typically arrives around 09/29, about 142 frost-free days later.
The USDA Plant Hardiness Zone Map puts Winthrop in Zone 6a (-10 to -5°F average annual minimum); frost dates are NOAA's 1991-2020 station normal, not this year's forecast.
What to do before the first frost
Zone 6a around Winthrop has about 5 weeks left before the first fall frost — that's the usual window to get a cold frame up if you want to keep harvesting past it.
Why 05/09 isn't a guarantee
05/09 is the middle of 30 years of NOAA records, not a promise. Plant by 04/28 and you're betting against frost in roughly 9 years out of 10. 05/24 is the safer bet, historically only a 1-in-10 chance of frost that late.
How Winthrop compares
About 142 days separate Winthrop's last and first frost, putting it 36,787 of 40,283 ZIP codes nationally. Within WA, it ranks 612 of 700.
Learn more
zone vs. frost date explains why Zone 6a and Winthrop's frost date answer different questions, and the frost range explains how to read the range around Winthrop's dates instead of trusting one.