El Cajon, CA 91901 Frost Dates
91901, near El Cajon, 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 12/24, roughly 317 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 El Cajon, not a forecast for this year.
Stretching the season past the first frost
El Cajon'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.
How much risk comes with planting early here
02/12 is the middle of 30 years of NOAA records, not a promise. Getting tender plants in by 03/20 carries real risk, frost has hit that late in about 9 of 10 years here. Wait until 12/29 and only about 1 year in 10 sees frost after that.
El Cajon against the rest of the dataset
About 317 days separate El Cajon's last and first frost, putting it 3,367 of 40,283 ZIP codes nationally. Within CA, it ranks 1,402 of 2,555.
Learn more
Two guides worth reading on 91901: the frost range, on how to read the range around El Cajon's dates instead of trusting one, and local microclimates, on what one yard in El Cajon can differ from the 91901 normal.