San Antonio, TX 78221 Frost Dates
78221, near San Antonio, TX: the frost window
The last spring frost here typically falls around 02/20, about 176 days from today. Fall's first freeze usually shows up around 12/03, roughly 291 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 San Antonio, not a forecast for this year.
Stretching the season past the first frost
San Antonio'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 02/20 isn't a guarantee
02/20 is the middle of 30 years of NOAA records, not a promise. Getting tender plants in by 01/20 carries real risk, frost has hit that late in about 9 of 10 years here. Wait until 03/13 and only about 1 year in 10 sees frost after that.
San Antonio against the rest of the dataset
About 291 days separate San Antonio's last and first frost, putting it 4,389 of 40,283 ZIP codes nationally. Within TX, it ranks 551 of 2,558.
Learn more
Two guides worth reading on 78221: local microclimates, on what one yard in San Antonio can differ from the 78221 normal, and zone vs. frost date, on why Zone 9a and San Antonio's frost date answer different questions.