Illiopolis, IL 62539 Frost Dates
Frost dates for Illiopolis, IL, ZIP 62539
Typically, the last spring freeze lands around 04/14, roughly 229 days out. The first fall frost typically arrives around 10/24, about 192 frost-free days later.
Illiopolis sits in USDA Zone 6a (-10 to -5°F average annual minimum). The dates above are NOAA's 1991-2020 normal at the nearest reporting station, a 30-year average, not a forecast.
What to do before the first frost
Zone 6a around Illiopolis 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.
How much risk comes with planting early here
04/14 is the middle of 30 years of NOAA records, not a promise. Plant by 04/01 and you're betting against frost in roughly 9 years out of 10. 05/01 is the safer bet, historically only a 1-in-10 chance of frost that late.
How Illiopolis compares
Illiopolis's growing season runs about 192 days, ranking 20,489 of 40,283 US ZIP codes measured here, longest to shortest. Within IL, it ranks 431 of 1,548.
Learn more
zone vs. frost date explains why Zone 6a and Illiopolis's frost date answer different questions, and the frost range explains how to read the range around Illiopolis's dates instead of trusting one.