Mill Valley, CA 94145 Frost Dates
94145, near Mill Valley, CA: the frost window
Typically, the last spring freeze lands around 12/30, roughly 124 days out. Fall's first freeze usually shows up around 12/25, roughly 365 days after the last spring frost.
The USDA Plant Hardiness Zone Map puts Mill Valley in Zone 10b (35 to 40°F average annual minimum); frost dates are NOAA's 1991-2020 station normal, not this year's forecast.
Stretching the season past the first frost
Mill Valley'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 12/30 isn't a guarantee
12/30 is the middle of 30 years of NOAA records, not a promise. Getting tender plants in by 03/13 carries real risk, frost has hit that late in about 9 of 10 years here. Wait until 12/02 and only about 1 year in 10 sees frost after that.
Mill Valley against the rest of the dataset
At roughly 365 frost-free days, Mill Valley places 1,660 of 40,283 ZIP codes in this dataset. Within CA, it ranks 805 of 2,555.
Learn more
Two guides worth reading on 94145: local microclimates, on what one yard in Mill Valley can differ from the 94145 normal, and zone vs. frost date, on why Zone 10b and Mill Valley's frost date answer different questions.