Lemont, IL 60439 Frost Dates
Frost dates for Lemont, IL, ZIP 60439
Around 04/19 is the usual last spring frost, about 234 days away. The first fall frost typically arrives around 10/22, about 183 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 Lemont, not a forecast for this year.
What to do before the first frost
Zone 6a around Lemont 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
04/19 is the middle of 30 years of NOAA records, not a promise. Plant by 04/06 and you're betting against frost in roughly 9 years out of 10. 05/05 is the safer bet, historically only a 1-in-10 chance of frost that late.
How Lemont compares
Lemont's growing season runs about 183 days, ranking 23,780 of 40,283 US ZIP codes measured here, longest to shortest. Within IL, it ranks 878 of 1,548.
Learn more
zone vs. frost date explains why Zone 6a and Lemont's frost date answer different questions, and the frost range explains how to read the range around Lemont's dates instead of trusting one.