El Cajon, CA 91905 Frost Dates
91905, near El Cajon, CA: the frost window
Typically, the last spring freeze lands around 04/29, roughly 244 days out. Fall's first freeze usually shows up around 11/01, roughly 184 days after the last spring frost.
El Cajon sits in USDA Zone 9a (20 to 25°F average annual minimum). The dates above are NOAA's 1991-2020 normal at the nearest reporting station, a 30-year average, not a forecast.
Stretching the season past the first frost
El Cajon's growing season runs out in roughly 9 weeks — a cold frame or greenhouse kit is the usual way to keep cool-weather crops going past the first frost.
Why 04/29 isn't a guarantee
04/29 is the middle of 30 years of NOAA records, not a promise. Getting tender plants in by 04/07 carries real risk, frost has hit that late in about 9 of 10 years here. Wait until 06/01 and only about 1 year in 10 sees frost after that.
El Cajon against the rest of the dataset
About 184 days separate El Cajon's last and first frost, putting it 23,390 of 40,283 ZIP codes nationally. Within CA, it ranks 2,329 of 2,555.
Learn more
Two guides worth reading on 91905: zone vs. frost date, on why Zone 9a and El Cajon's frost date answer different questions, and the frost range, on how to read the range around El Cajon's dates instead of trusting one.