Alhambra, CA 91803 Frost Dates
91803, near Alhambra, CA: the frost window
Typically, the last spring freeze lands around 01/04, roughly 129 days out. Fall's first freeze usually shows up around 01/02, 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 Alhambra, not a forecast for this year.
Stretching the season past the first frost
Alhambra's growing season runs out in roughly 18 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 Alhambra's last frost
01/04 is the middle of 30 years of NOAA records, not a promise. Getting tender plants in by 01/28 carries real risk, frost has hit that late in about 9 of 10 years here. Wait until 12/19 and only about 1 year in 10 sees frost after that.
Alhambra against the rest of the dataset
At roughly 365 frost-free days, Alhambra places 681 of 40,283 ZIP codes in this dataset. Within CA, it ranks 298 of 2,555.
Learn more
Two guides worth reading on 91803: the frost range, on how to read the range around Alhambra's dates instead of trusting one, and local microclimates, on what one yard in Alhambra can differ from the 91803 normal.