Rialto, CA 92377 Frost Dates
Rialto, CA: when does the frost end?
Around 01/10 is the usual last spring frost, about 135 days away. Fall's first freeze usually shows up around 01/02, roughly 365 days after the last spring frost.
The USDA Plant Hardiness Zone Map puts Rialto in Zone 10a (30 to 35°F average annual minimum); frost dates are NOAA's 1991-2020 station normal, not this year's forecast.
Stretching the season past the first frost
With roughly 18 weeks until Rialto's first fall frost, a row cover or cold frame is what stretches the last few weeks of harvest here.
How much risk comes with planting early here
01/10 is the middle of 30 years of NOAA records, not a promise. Getting tender plants in by 02/17 carries real risk, frost has hit that late in about 9 of 10 years here. Wait until 12/20 and only about 1 year in 10 sees frost after that.
Rialto against the rest of the dataset
At roughly 365 frost-free days, Rialto places 486 of 40,283 ZIP codes in this dataset. Within CA, it ranks 202 of 2,555.
Learn more
Before leaning on 92377's figures: the frost range explains how to read the range around Rialto's dates instead of trusting one, while local microclimates explains what one yard in Rialto can differ from the 92377 normal.