Mill Valley, CA 94139 Frost Dates
When can you plant in Mill Valley, CA?
The last spring frost here typically falls around 12/30, about 124 days from today. 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.
The actual range around Mill Valley's last frost
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
About 365 days separate Mill Valley's last and first frost, putting it 1,655 of 40,283 ZIP codes nationally. Within CA, it ranks 800 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.