Mill Valley, CA 94137 Frost Dates
Frost dates for Mill Valley, CA, ZIP 94137
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.
Zone 10b (35 to 40°F average annual minimum) comes from the USDA Plant Hardiness Zone Map; the frost dates above are the 1991-2020 normal at the nearest reporting NOAA station for Mill Valley, not a forecast for this year.
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.
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 1,654 of 40,283 ZIP codes nationally. Within CA, it ranks 799 of 2,555.
Learn more
local microclimates explains what one yard in Mill Valley can differ from the 94137 normal, and zone vs. frost date explains why Zone 10b and Mill Valley's frost date answer different questions.