Portola, CA 96103 Frost Dates
Frost dates for Portola, CA, ZIP 96103
Typically, the last spring freeze lands around 06/11, roughly 287 days out. The first fall frost typically arrives around 09/10, about 91 frost-free days later.
Zone 7a (0 to 5°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 Portola, not a forecast for this year.
What to do before the first frost
Zone 7a around Portola has about 2 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.
Why 06/11 isn't a guarantee
06/11 is the middle of 30 years of NOAA records, not a promise. Plant by 05/25 and you're betting against frost in roughly 9 years out of 10. 07/02 is the safer bet, historically only a 1-in-10 chance of frost that late.
How Portola compares
About 91 days separate Portola's last and first frost, putting it 39,898 of 40,283 ZIP codes nationally. Within CA, it ranks 2,532 of 2,555.
Learn more
local microclimates explains what one yard in Portola can differ from the 96103 normal, and zone vs. frost date explains why Zone 7a and Portola's frost date answer different questions.