El Cajon, CA 91931 Frost Dates
Frost dates for El Cajon, CA, ZIP 91931
Typically, the last spring freeze lands around 04/19, roughly 234 days out. The first fall frost typically arrives around 10/27, about 190 frost-free days later.
El Cajon sits in USDA Zone 8b (15 to 20°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.
What to do before the first frost
Zone 8b around El Cajon has about 9 weeks left before the first fall frost — that's the usual window to get a cold frame up if you want to keep harvesting past it.
Why 04/19 isn't a guarantee
04/19 is the middle of 30 years of NOAA records, not a promise. Plant by 03/24 and you're betting against frost in roughly 9 years out of 10. 05/14 is the safer bet, historically only a 1-in-10 chance of frost that late.
How El Cajon compares
About 190 days separate El Cajon's last and first frost, putting it 20,979 of 40,283 ZIP codes nationally. Within CA, it ranks 2,312 of 2,555.
Learn more
local microclimates explains what one yard in El Cajon can differ from the 91931 normal, and zone vs. frost date explains why Zone 8b and El Cajon's frost date answer different questions.