Rialto, CA 92376 Frost Dates
When can you plant in Rialto, CA?
Around 01/10 is the usual last spring frost, about 135 days away. 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
About 18 weeks of growing season left in Rialto before the first fall frost — a cold frame or row cover can stretch harvest weeks past that date.
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
Rialto's growing season runs about 365 days, ranking 485 of 40,283 US ZIP codes measured here, longest to shortest. Within CA, it ranks 201 of 2,555.
Learn more
zone vs. frost date covers why Zone 10a and Rialto's frost date answer different questions. the frost range covers how to read the range around Rialto's dates instead of trusting one.