Brentwood, CA 94531 Frost Dates
Frost dates for Brentwood, CA, ZIP 94531
Around 01/12 is the usual last spring frost, about 137 days away. The first fall frost typically arrives around 12/19, about 343 frost-free days later.
Brentwood sits in USDA Zone 9b (25 to 30°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 9b around Brentwood has about 16 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
01/12 is the middle of 30 years of NOAA records, not a promise. Plant by 02/01 and you're betting against frost in roughly 9 years out of 10. 12/20 is the safer bet, historically only a 1-in-10 chance of frost that late.
How Brentwood compares
About 343 days separate Brentwood's last and first frost, putting it 2,524 of 40,283 ZIP codes nationally. Within CA, it ranks 1,113 of 2,555.
Learn more
zone vs. frost date explains why Zone 9b and Brentwood's frost date answer different questions, and the frost range explains how to read the range around Brentwood's dates instead of trusting one.