Sonoma, CA 95433 Frost Dates
Sonoma, CA: when does the frost end?
Around 03/02 is the usual last spring frost, about 186 days away. Fall's first freeze usually shows up around 11/27, roughly 270 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 Sonoma, not a forecast for this year.
Stretching the season past the first frost
With roughly 13 weeks until Sonoma's first fall frost, a row cover or cold frame is what stretches the last few weeks of harvest here.
Why 03/02 isn't a guarantee
03/02 is the middle of 30 years of NOAA records, not a promise. Getting tender plants in by 01/27 carries real risk, frost has hit that late in about 9 of 10 years here. Wait until 04/05 and only about 1 year in 10 sees frost after that.
Sonoma against the rest of the dataset
At roughly 270 frost-free days, Sonoma places 5,563 of 40,283 ZIP codes in this dataset. Within CA, it ranks 1,975 of 2,555.
Learn more
Before leaning on 95433's figures: zone vs. frost date explains why Zone 9b and Sonoma's frost date answer different questions, while the frost range explains how to read the range around Sonoma's dates instead of trusting one.