Black Diamond, WA 98010 Frost Dates
Frost dates for Black Diamond, WA, ZIP 98010
Around 04/20 is the usual last spring frost, about 235 days away. The first fall frost typically arrives around 10/25, about 187 frost-free days later.
Black Diamond sits in USDA Zone 8b (15 to 20°F average annual minimum). The dates above are NOAA's 1991-2020 normal at the nearest reporting station, a 30-year average, not a forecast.
What to do before the first frost
Zone 8b around Black Diamond 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 04/20 isn't a guarantee
04/20 is the middle of 30 years of NOAA records, not a promise. Plant by 03/31 and you're betting against frost in roughly 9 years out of 10. 05/10 is the safer bet, historically only a 1-in-10 chance of frost that late.
How Black Diamond compares
About 187 days separate Black Diamond's last and first frost, putting it 22,345 of 40,283 ZIP codes nationally. Within WA, it ranks 421 of 700.
Learn more
local microclimates explains what one yard in Black Diamond can differ from the 98010 normal, and zone vs. frost date explains why Zone 8b and Black Diamond's frost date answer different questions.