Irvine, CA 92603 Frost Dates
92603, near Irvine, CA: the frost window
Typically, the last spring freeze lands around 01/05, roughly 130 days out. Fall's first freeze usually shows up around 12/25, roughly 365 days after the last spring frost.
Zone 10b (35 to 40°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 Irvine, not a forecast for this year.
Stretching the season past the first frost
Irvine's growing season runs out in roughly 17 weeks — a cold frame or greenhouse kit is the usual way to keep cool-weather crops going past the first frost.
Why 01/05 isn't a guarantee
01/05 is the middle of 30 years of NOAA records, not a promise. Getting tender plants in by 02/02 carries real risk, frost has hit that late in about 9 of 10 years here. Wait until 12/14 and only about 1 year in 10 sees frost after that.
Irvine against the rest of the dataset
About 365 days separate Irvine's last and first frost, putting it 246 of 40,283 ZIP codes nationally. Within CA, it ranks 41 of 2,555.
Learn more
Two guides worth reading on 92603: zone vs. frost date, on why Zone 10b and Irvine's frost date answer different questions, and the frost range, on how to read the range around Irvine's dates instead of trusting one.