Mill Valley, CA 94142 Frost Dates
Frost dates for Mill Valley, CA, ZIP 94142
Around 12/30 is the usual last spring frost, about 124 days away. The first fall frost typically arrives around 12/25, about 365 frost-free days later.
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.
What to do before the first frost
Zone 10b around Mill Valley has about 17 weeks left before the first fall frost — that's the usual window to get a cold frame up if you want to keep harvesting past it.
How much risk comes with planting early here
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 1,658 of 40,283 ZIP codes nationally. Within CA, it ranks 803 of 2,555.
Learn more
the frost range explains how to read the range around Mill Valley's dates instead of trusting one, and local microclimates explains what one yard in Mill Valley can differ from the 94142 normal.