Porterville, CA 93278 Frost Dates
93278, near Porterville, CA: the frost window
The last spring frost here typically falls around 02/20, about 176 days from today. Fall's first freeze usually shows up around 11/30, roughly 284 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 Porterville, not a forecast for this year.
Stretching the season past the first frost
Porterville's growing season runs out in roughly 13 weeks — a cold frame or greenhouse kit is the usual way to keep cool-weather crops going past the first frost.
Why 02/20 isn't a guarantee
02/20 is the middle of 30 years of NOAA records, not a promise. Getting tender plants in by 01/20 carries real risk, frost has hit that late in about 9 of 10 years here. Wait until 03/26 and only about 1 year in 10 sees frost after that.
Porterville against the rest of the dataset
About 284 days separate Porterville's last and first frost, putting it 4,675 of 40,283 ZIP codes nationally. Within CA, it ranks 1,732 of 2,555.
Learn more
Two guides worth reading on 93278: local microclimates, on what one yard in Porterville can differ from the 93278 normal, and zone vs. frost date, on why Zone 9b and Porterville's frost date answer different questions.