St. Helena, CA 94574 Frost Dates
Frost dates for St. Helena, CA, ZIP 94574
Typically, the last spring freeze lands around 02/03, roughly 159 days out. The first fall frost typically arrives around 12/04, about 306 frost-free days later.
The USDA Plant Hardiness Zone Map puts St. Helena 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 St. Helena has about 14 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 St. Helena's last frost
02/03 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. 12/28 is the safer bet, historically only a 1-in-10 chance of frost that late.
How St. Helena compares
About 306 days separate St. Helena's last and first frost, putting it 3,690 of 40,283 ZIP codes nationally. Within CA, it ranks 1,498 of 2,555.
Learn more
the frost range explains how to read the range around St. Helena's dates instead of trusting one, and local microclimates explains what one yard in St. Helena can differ from the 94574 normal.