Poway, CA 92178 Frost Dates
92178, near Poway, CA: the frost window
Typically, the last spring freeze lands around 03/04, roughly 188 days out. Fall's first freeze usually shows up around 12/04, roughly 270 days after the last spring frost.
Poway sits in USDA Zone 10b (35 to 40°F average annual minimum). The dates above are NOAA's 1991-2020 normal at the nearest reporting station, a 30-year average, not a forecast.
Stretching the season past the first frost
Poway's growing season runs out in roughly 14 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 01/29 carries real risk, frost has hit that late in about 9 of 10 years here. Wait until 04/10 and only about 1 year in 10 sees frost after that.
Poway against the rest of the dataset
At roughly 270 frost-free days, Poway places 5,544 of 40,283 ZIP codes in this dataset. Within CA, it ranks 1,964 of 2,555.
Learn more
Two guides worth reading on 92178: zone vs. frost date, on why Zone 10b and Poway's frost date answer different questions, and the frost range, on how to read the range around Poway's dates instead of trusting one.