El Monte, CA 91731 Frost Dates
Frost dates for El Monte, CA, ZIP 91731
Around 01/04 is the usual last spring frost, about 129 days away. The first fall frost typically arrives around 01/02, about 365 frost-free days later.
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 El Monte, not a forecast for this year.
What to do before the first frost
Zone 10b around El Monte has about 18 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.
The actual range around El Monte's last frost
01/04 is the middle of 30 years of NOAA records, not a promise. Plant by 01/28 and you're betting against frost in roughly 9 years out of 10. 12/19 is the safer bet, historically only a 1-in-10 chance of frost that late.
How El Monte compares
About 365 days separate El Monte's last and first frost, putting it 487 of 40,283 ZIP codes nationally. Within CA, it ranks 203 of 2,555.
Learn more
local microclimates explains what one yard in El Monte can differ from the 91731 normal, and zone vs. frost date explains why Zone 10b and El Monte's frost date answer different questions.