St. Helena, CA 94581 Frost Dates
Frost dates for St. Helena, CA, ZIP 94581
The last spring frost here typically falls around 02/03, about 159 days from today. The first fall frost typically arrives around 12/04, about 306 frost-free days later.
St. Helena sits in USDA Zone 9b (25 to 30°F average annual minimum). The dates above are NOAA's 1991-2020 normal at the nearest reporting station, a 30-year average, not a 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
St. Helena's growing season runs about 306 days, ranking 3,691 of 40,283 US ZIP codes measured here, longest to shortest. Within CA, it ranks 1,499 of 2,555.
Learn more
zone vs. frost date explains why Zone 9b and St. Helena's frost date answer different questions, and the frost range explains how to read the range around St. Helena's dates instead of trusting one.