San Juan, TX 78589 Frost Dates
Frost dates for San Juan, TX, ZIP 78589
Around 01/09 is the usual last spring frost, about 134 days away. The first fall frost typically arrives around 01/03, about 365 frost-free days later.
The USDA Plant Hardiness Zone Map puts San Juan in Zone 10a (30 to 35°F average annual minimum); frost dates are NOAA's 1991-2020 station normal, not this year's forecast.
What to do before the first frost
Zone 10a around San Juan has about 18 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.
The actual range around San Juan's last frost
01/09 is the middle of 30 years of NOAA records, not a promise. Plant by 02/13 and you're betting against frost in roughly 9 years out of 10. 12/17 is the safer bet, historically only a 1-in-10 chance of frost that late.
How San Juan compares
At roughly 365 frost-free days, San Juan places 994 of 40,283 ZIP codes in this dataset. Within TX, it ranks 24 of 2,558.
Learn more
zone vs. frost date explains why Zone 10a and San Juan's frost date answer different questions, and the frost range explains how to read the range around San Juan's dates instead of trusting one.