Rock Island, WA 98828 Frost Dates
Frost dates for Rock Island, WA, ZIP 98828
Typically, the last spring freeze lands around 04/08, roughly 223 days out. The first fall frost typically arrives around 10/24, about 200 frost-free days later.
Zone 7a (0 to 5°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 Rock Island, not a forecast for this year.
What to do before the first frost
Zone 7a around Rock Island has about 8 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 04/08 isn't a guarantee
04/08 is the middle of 30 years of NOAA records, not a promise. Plant by 03/20 and you're betting against frost in roughly 9 years out of 10. 04/23 is the safer bet, historically only a 1-in-10 chance of frost that late.
How Rock Island compares
Rock Island's growing season runs about 200 days, ranking 17,824 of 40,283 US ZIP codes measured here, longest to shortest. Within WA, it ranks 324 of 700.
Learn more
local microclimates explains what one yard in Rock Island can differ from the 98828 normal, and zone vs. frost date explains why Zone 7a and Rock Island's frost date answer different questions.