Alton, IN 40104 Frost Dates
Frost dates for Alton, IN, ZIP 40104
Typically, the last spring freeze lands around 04/19, roughly 234 days out. The first fall frost typically arrives around 10/24, about 186 frost-free days later.
Zone 7a (0 to 5°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 Alton, not a forecast for this year.
What to do before the first frost
Zone 7a around Alton has about 8 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 04/19 isn't a guarantee
04/19 is the middle of 30 years of NOAA records, not a promise. Plant by 04/04 and you're betting against frost in roughly 9 years out of 10. 05/02 is the safer bet, historically only a 1-in-10 chance of frost that late.
How Alton compares
About 186 days separate Alton's last and first frost, putting it 22,988 of 40,283 ZIP codes nationally. Within IN, it ranks 351 of 927.
Learn more
zone vs. frost date explains why Zone 7a and Alton's frost date answer different questions, and the frost range explains how to read the range around Alton's dates instead of trusting one.