Napa, CA 94558 Frost Dates
94558, near Napa, CA: the frost window
The last spring frost here typically falls around 02/12, about 168 days from today. Fall's first freeze usually shows up around 12/04, roughly 299 days after the last spring frost.
Zone 9b (25 to 30°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 Napa, not a forecast for this year.
Stretching the season past the first frost
Napa's growing season runs out in roughly 14 weeks — a cold frame or greenhouse kit is the usual way to keep cool-weather crops going past the first frost.
The actual range around Napa's last frost
02/12 is the middle of 30 years of NOAA records, not a promise. Getting tender plants in by 01/03 carries real risk, frost has hit that late in about 9 of 10 years here. Wait until 03/13 and only about 1 year in 10 sees frost after that.
Napa against the rest of the dataset
Napa's growing season runs about 299 days, ranking 4,152 of 40,283 US ZIP codes measured here, longest to shortest. Within CA, it ranks 1,639 of 2,555.
Learn more
Two guides worth reading on 94558: local microclimates, on what one yard in Napa can differ from the 94558 normal, and zone vs. frost date, on why Zone 9b and Napa's frost date answer different questions.