Sonora, CA 95309 Frost Dates
Frost dates for Sonora, CA, ZIP 95309
Typically, the last spring freeze lands around 04/09, roughly 224 days out. The first fall frost typically arrives around 11/09, about 213 frost-free days later.
The USDA Plant Hardiness Zone Map puts Sonora in Zone 9b (25 to 30°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 9b around Sonora has about 10 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 04/09 isn't a guarantee
04/09 is the middle of 30 years of NOAA records, not a promise. Plant by 03/15 and you're betting against frost in roughly 9 years out of 10. 04/30 is the safer bet, historically only a 1-in-10 chance of frost that late.
How Sonora compares
At roughly 213 frost-free days, Sonora places 14,492 of 40,283 ZIP codes in this dataset. Within CA, it ranks 2,196 of 2,555.
Learn more
the frost range explains how to read the range around Sonora's dates instead of trusting one, and local microclimates explains what one yard in Sonora can differ from the 95309 normal.