Poway, CA 91921 Frost Dates
Frost dates for Poway, CA, ZIP 91921
Around 03/04 is the usual last spring frost, about 188 days away. The first fall frost typically arrives around 12/04, about 270 frost-free days later.
Zone 10b (35 to 40°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 Poway, not a forecast for this year.
What to do before the first frost
Zone 10b around Poway has about 14 weeks left before the first fall frost — that's the usual window to get a cold frame up if you want to keep harvesting past it.
Why 03/04 isn't a guarantee
03/04 is the middle of 30 years of NOAA records, not a promise. Plant by 01/29 and you're betting against frost in roughly 9 years out of 10. 04/10 is the safer bet, historically only a 1-in-10 chance of frost that late.
How Poway compares
Poway's growing season runs about 270 days, ranking 5,485 of 40,283 US ZIP codes measured here, longest to shortest. Within CA, it ranks 1,905 of 2,555.
Learn more
the frost range explains how to read the range around Poway's dates instead of trusting one, and local microclimates explains what one yard in Poway can differ from the 91921 normal.