Los Altos, CA 94040 Frost Dates
94040, near Los Altos, CA: the frost window
The last spring frost here typically falls around 01/06, about 131 days from today. Fall's first freeze usually shows up around 12/23, roughly 353 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 Los Altos, not a forecast for this year.
Stretching the season past the first frost
Los Altos'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.
Why 01/06 isn't a guarantee
01/06 is the middle of 30 years of NOAA records, not a promise. Getting tender plants in by 02/04 carries real risk, frost has hit that late in about 9 of 10 years here. Wait until 12/16 and only about 1 year in 10 sees frost after that.
Los Altos against the rest of the dataset
At roughly 353 frost-free days, Los Altos places 2,227 of 40,283 ZIP codes in this dataset. Within CA, it ranks 1,003 of 2,555.
Learn more
Two guides worth reading on 94040: zone vs. frost date, on why Zone 9b and Los Altos's frost date answer different questions, and the frost range, on how to read the range around Los Altos's dates instead of trusting one.