Mill Valley, CA 94188 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.
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
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
About 365 days separate Mill Valley's last and first frost, putting it 1,671 of 40,283 ZIP codes nationally. Within CA, it ranks 816 of 2,555.
Learn more
the frost range covers how to read the range around Mill Valley's dates instead of trusting one. local microclimates covers what one yard in Mill Valley can differ from the 94188 normal.