Castle Rock, WA 98645 Frost Dates
Frost dates for Castle Rock, WA, ZIP 98645
Around 04/05 is the usual last spring frost, about 220 days away. The first fall frost typically arrives around 10/25, about 196 frost-free days later.
The USDA Plant Hardiness Zone Map puts Castle Rock 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 Castle Rock 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.
How much risk comes with planting early here
04/05 is the middle of 30 years of NOAA records, not a promise. Plant by 03/12 and you're betting against frost in roughly 9 years out of 10. 05/04 is the safer bet, historically only a 1-in-10 chance of frost that late.
How Castle Rock compares
Castle Rock's growing season runs about 196 days, ranking 18,993 of 40,283 US ZIP codes measured here, longest to shortest. Within WA, it ranks 350 of 700.
Learn more
zone vs. frost date explains why Zone 8b and Castle Rock's frost date answer different questions, and the frost range explains how to read the range around Castle Rock's dates instead of trusting one.