Coos Bay, OR 97420 Frost Dates
Frost dates for Coos Bay, OR, ZIP 97420
Around 02/21 is the usual last spring frost, about 177 days away. The first fall frost typically arrives around 12/09, about 294 frost-free days later.
Zone 9a (20 to 25°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 Coos Bay, not a forecast for this year.
What to do before the first frost
Zone 9a around Coos Bay has about 15 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 02/21 isn't a guarantee
02/21 is the middle of 30 years of NOAA records, not a promise. Plant by 03/25 and you're betting against frost in roughly 9 years out of 10. 12/31 is the safer bet, historically only a 1-in-10 chance of frost that late.
How Coos Bay compares
At roughly 294 frost-free days, Coos Bay places 4,260 of 40,283 ZIP codes in this dataset. Within OR, it ranks 31 of 463.
Learn more
zone vs. frost date explains why Zone 9a and Coos Bay's frost date answer different questions, and the frost range explains how to read the range around Coos Bay's dates instead of trusting one.