Forest Grove, OR 97291 Frost Dates
Frost dates for Forest Grove, OR, ZIP 97291
Around 04/16 is the usual last spring frost, about 231 days away. The first fall frost typically arrives around 10/26, about 192 frost-free days later.
Zone 8b (15 to 20°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 Forest Grove, not a forecast for this year.
What to do before the first frost
Zone 8b around Forest Grove 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 04/16 isn't a guarantee
04/16 is the middle of 30 years of NOAA records, not a promise. Plant by 03/26 and you're betting against frost in roughly 9 years out of 10. 05/05 is the safer bet, historically only a 1-in-10 chance of frost that late.
How Forest Grove compares
At roughly 192 frost-free days, Forest Grove places 20,183 of 40,283 ZIP codes in this dataset. Within OR, it ranks 269 of 463.
Learn more
zone vs. frost date explains why Zone 8b and Forest Grove's frost date answer different questions, and the frost range explains how to read the range around Forest Grove's dates instead of trusting one.