Clayton, CA 94527 Frost Dates
94527, near Clayton, CA: the frost window
Around 03/08 is the usual last spring frost, about 192 days away. Fall's first freeze usually shows up around 12/22, roughly 282 days after the last spring frost.
Zone 9b (25 to 30°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 Clayton, not a forecast for this year.
Stretching the season past the first frost
Clayton's growing season runs out in roughly 17 weeks — a cold frame or greenhouse kit is the usual way to keep cool-weather crops going past the first frost.
The actual range around Clayton's last frost
03/08 is the middle of 30 years of NOAA records, not a promise. Getting tender plants in by 01/12 carries real risk, frost has hit that late in about 9 of 10 years here. Wait until 04/15 and only about 1 year in 10 sees frost after that.
Clayton against the rest of the dataset
About 282 days separate Clayton's last and first frost, putting it 4,780 of 40,283 ZIP codes nationally. Within CA, it ranks 1,764 of 2,555.
Learn more
Two guides worth reading on 94527: local microclimates, on what one yard in Clayton can differ from the 94527 normal, and zone vs. frost date, on why Zone 9b and Clayton's frost date answer different questions.