Grass Valley, CA 95975 Frost Dates
95975, near Grass Valley, CA: the frost window
Typically, the last spring freeze lands around 04/10, roughly 225 days out. Fall's first freeze usually shows up around 11/13, roughly 215 days after the last spring frost.
The USDA Plant Hardiness Zone Map puts Grass Valley in Zone 9a (20 to 25°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
Grass Valley's growing season runs out in roughly 11 weeks — a cold frame or greenhouse kit is the usual way to keep cool-weather crops going past the first frost.
Why 04/10 isn't a guarantee
04/10 is the middle of 30 years of NOAA records, not a promise. Getting tender plants in by 03/17 carries real risk, frost has hit that late in about 9 of 10 years here. Wait until 04/30 and only about 1 year in 10 sees frost after that.
Grass Valley against the rest of the dataset
About 215 days separate Grass Valley's last and first frost, putting it 14,050 of 40,283 ZIP codes nationally. Within CA, it ranks 2,189 of 2,555.
Learn more
Two guides worth reading on 95975: zone vs. frost date, on why Zone 9a and Grass Valley's frost date answer different questions, and the frost range, on how to read the range around Grass Valley's dates instead of trusting one.