Mill Valley, CA 94126 Frost Dates
When can you plant in Mill Valley, CA?
Typically, the last spring freeze lands around 12/30, roughly 124 days out. The first fall frost typically arrives around 12/25, about 365 frost-free days later.
Mill Valley sits in USDA Zone 10b (35 to 40°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.
What to do before the first frost
About 17 weeks of growing season left in Mill Valley before the first fall frost — a cold frame or row cover can stretch harvest weeks past that date.
Why 12/30 isn't a guarantee
12/30 is the middle of 30 years of NOAA records, not a promise. Plant by 03/13 and you're betting against frost in roughly 9 years out of 10. 12/02 is the safer bet, historically only a 1-in-10 chance of frost that late.
How Mill Valley compares
Mill Valley's growing season runs about 365 days, ranking 1,653 of 40,283 US ZIP codes measured here, longest to shortest. Within CA, it ranks 798 of 2,555.
Learn more
zone vs. frost date covers why Zone 10b and Mill Valley's frost date answer different questions. the frost range covers how to read the range around Mill Valley's dates instead of trusting one.