Rialto, CA 92316 Frost Dates
Frost dates for Rialto, CA, ZIP 92316
The last spring frost here typically falls around 01/10, about 135 days from today. The first fall frost typically arrives around 01/02, about 365 frost-free days later.
Zone 10a (30 to 35°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 Rialto, not a forecast for this year.
What to do before the first frost
Zone 10a around Rialto 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.
How much risk comes with planting early here
01/10 is the middle of 30 years of NOAA records, not a promise. Plant by 02/17 and you're betting against frost in roughly 9 years out of 10. 12/20 is the safer bet, historically only a 1-in-10 chance of frost that late.
How Rialto compares
About 365 days separate Rialto's last and first frost, putting it 484 of 40,283 ZIP codes nationally. Within CA, it ranks 200 of 2,555.
Learn more
local microclimates explains what one yard in Rialto can differ from the 92316 normal, and zone vs. frost date explains why Zone 10a and Rialto's frost date answer different questions.