El Cajon, CA 91978 Frost Dates
91978, near El Cajon, CA: the frost window
The last spring frost here typically falls around 01/06, about 131 days from today. Fall's first freeze usually shows up around 12/21, roughly 350 days after the last spring frost.
El Cajon sits in USDA Zone 10b (35 to 40°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 16 weeks — a cold frame or greenhouse kit is the usual way to keep cool-weather crops going past the first frost.
Why 01/06 isn't a guarantee
01/06 is the middle of 30 years of NOAA records, not a promise. Getting tender plants in by 02/07 carries real risk, frost has hit that late in about 9 of 10 years here. Wait until 12/13 and only about 1 year in 10 sees frost after that.
El Cajon against the rest of the dataset
About 350 days separate El Cajon's last and first frost, putting it 2,317 of 40,283 ZIP codes nationally. Within CA, it ranks 1,023 of 2,555.
Learn more
Two guides worth reading on 91978: 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 91978 normal.