Portola Valley, CA 94021 Frost Dates
Portola Valley, CA: when does the frost end?
The last spring frost here typically falls around 03/02, about 186 days from today. Fall's first freeze usually shows up around 11/25, roughly 268 days after the last spring frost.
Portola Valley 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.
Stretching the season past the first frost
With roughly 13 weeks until Portola Valley'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 04/15 carries real risk, frost has hit that late in about 9 of 10 years here. Wait until 12/31 and only about 1 year in 10 sees frost after that.
Portola Valley against the rest of the dataset
At roughly 268 frost-free days, Portola Valley places 5,763 of 40,283 ZIP codes in this dataset. Within CA, it ranks 1,987 of 2,555.
Learn more
Before leaning on 94021's figures: the frost range explains how to read the range around Portola Valley's dates instead of trusting one, while local microclimates explains what one yard in Portola Valley can differ from the 94021 normal.