St. Helena, CA 94508 Frost Dates
St. Helena, CA: when does the frost end?
The last spring frost here typically falls around 04/07, about 222 days from today. Fall's first freeze usually shows up around 12/05, roughly 245 days after the last spring frost.
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.
Stretching the season past the first frost
With roughly 14 weeks until St. Helena's first fall frost, a row cover or cold frame is what stretches the last few weeks of harvest here.
Why 04/07 isn't a guarantee
04/07 is the middle of 30 years of NOAA records, not a promise. Getting tender plants in by 02/23 carries real risk, frost has hit that late in about 9 of 10 years here. Wait until 04/30 and only about 1 year in 10 sees frost after that.
St. Helena against the rest of the dataset
About 245 days separate St. Helena's last and first frost, putting it 8,014 of 40,283 ZIP codes nationally. Within CA, it ranks 2,104 of 2,555.
Learn more
Before leaning on 94508's figures: the frost range explains how to read the range around St. Helena's dates instead of trusting one, while local microclimates explains what one yard in St. Helena can differ from the 94508 normal.