Rio Grande City, TX 78582 Frost Dates
Frost dates for Rio Grande City, TX, ZIP 78582
Around 01/31 is the usual last spring frost, about 156 days away. The first fall frost typically arrives around 12/17, about 321 frost-free days later.
Zone 9b (25 to 30°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 Grande City, not a forecast for this year.
What to do before the first frost
Zone 9b around Rio Grande City has about 16 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 01/31 isn't a guarantee
01/31 is the middle of 30 years of NOAA records, not a promise. Plant by 03/04 and you're betting against frost in roughly 9 years out of 10. 12/29 is the safer bet, historically only a 1-in-10 chance of frost that late.
How Rio Grande City compares
About 321 days separate Rio Grande City's last and first frost, putting it 3,293 of 40,283 ZIP codes nationally. Within TX, it ranks 208 of 2,558.
Learn more
zone vs. frost date explains why Zone 9b and Rio Grande City's frost date answer different questions, and the frost range explains how to read the range around Rio Grande City's dates instead of trusting one.