Mill Valley, CA 94970 Frost Dates
94970, near Mill Valley, CA: the frost window
Typically, the last spring freeze lands around 01/16, roughly 141 days out. Fall's first freeze usually shows up around 12/18, roughly 334 days after the last spring frost.
Mill Valley sits in USDA Zone 10a (30 to 35°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
Mill Valley's growing season runs out in roughly 16 weeks — a cold frame or greenhouse kit is the usual way to keep cool-weather crops going past the first frost.
How much risk comes with planting early here
01/16 is the middle of 30 years of NOAA records, not a promise. Getting tender plants in by 02/25 carries real risk, frost has hit that late in about 9 of 10 years here. Wait until 12/21 and only about 1 year in 10 sees frost after that.
Mill Valley against the rest of the dataset
About 334 days separate Mill Valley's last and first frost, putting it 2,790 of 40,283 ZIP codes nationally. Within CA, it ranks 1,274 of 2,555.
Learn more
Two guides worth reading on 94970: the frost range, on how to read the range around Mill Valley's dates instead of trusting one, and local microclimates, on what one yard in Mill Valley can differ from the 94970 normal.