Cosmopolis, WA 98537 Frost Dates
Frost dates for Cosmopolis, WA, ZIP 98537
Around 03/29 is the usual last spring frost, about 213 days away. The first fall frost typically arrives around 11/15, about 234 frost-free days later.
The USDA Plant Hardiness Zone Map puts Cosmopolis in Zone 8b (15 to 20°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 8b around Cosmopolis has about 11 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.
The actual range around Cosmopolis's last frost
03/29 is the middle of 30 years of NOAA records, not a promise. Plant by 02/25 and you're betting against frost in roughly 9 years out of 10. 04/20 is the safer bet, historically only a 1-in-10 chance of frost that late.
How Cosmopolis compares
At roughly 234 frost-free days, Cosmopolis places 9,757 of 40,283 ZIP codes in this dataset. Within WA, it ranks 170 of 700.
Learn more
zone vs. frost date explains why Zone 8b and Cosmopolis's frost date answer different questions, and the frost range explains how to read the range around Cosmopolis's dates instead of trusting one.