Charleston, IL 61920 Frost Dates
Frost dates for Charleston, IL, ZIP 61920
Around 04/15 is the usual last spring frost, about 230 days away. The first fall frost typically arrives around 10/23, about 187 frost-free days later.
Zone 6a (-10 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 Charleston, not a forecast for this year.
What to do before the first frost
Zone 6a around Charleston 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 04/15 isn't a guarantee
04/15 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. 05/03 is the safer bet, historically only a 1-in-10 chance of frost that late.
How Charleston compares
Charleston's growing season runs about 187 days, ranking 22,307 of 40,283 US ZIP codes measured here, longest to shortest. Within IL, it ranks 715 of 1,548.
Learn more
zone vs. frost date explains why Zone 6a and Charleston's frost date answer different questions, and the frost range explains how to read the range around Charleston's dates instead of trusting one.