Rio Dell, CA 95526 Frost Dates
95526, near Rio Dell, CA: the frost window
Around 03/04 is the usual last spring frost, about 188 days away. Fall's first freeze usually shows up around 11/22, roughly 264 days after the last spring frost.
Zone 9a (20 to 25°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 Rio Dell, not a forecast for this year.
Stretching the season past the first frost
Rio Dell's growing season runs out in roughly 12 weeks — a cold frame or greenhouse kit is the usual way to keep cool-weather crops going past the first frost.
Why 03/04 isn't a guarantee
03/04 is the middle of 30 years of NOAA records, not a promise. Getting tender plants in by 01/27 carries real risk, frost has hit that late in about 9 of 10 years here. Wait until 04/08 and only about 1 year in 10 sees frost after that.
Rio Dell against the rest of the dataset
Rio Dell's growing season runs about 264 days, ranking 6,063 of 40,283 US ZIP codes measured here, longest to shortest. Within CA, it ranks 2,004 of 2,555.
Learn more
Two guides worth reading on 95526: zone vs. frost date, on why Zone 9a and Rio Dell's frost date answer different questions, and the frost range, on how to read the range around Rio Dell's dates instead of trusting one.