Winnebago, IL 61105 Frost Dates
Frost dates for Winnebago, IL, ZIP 61105
Typically, the last spring freeze lands around 04/24, roughly 239 days out. The first fall frost typically arrives around 10/17, about 174 frost-free days later.
Zone 5b (-15 to -10°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 Winnebago, not a forecast for this year.
What to do before the first frost
Zone 5b around Winnebago has about 7 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
04/24 is the middle of 30 years of NOAA records, not a promise. Plant by 04/10 and you're betting against frost in roughly 9 years out of 10. 05/08 is the safer bet, historically only a 1-in-10 chance of frost that late.
How Winnebago compares
Winnebago's growing season runs about 174 days, ranking 27,478 of 40,283 US ZIP codes measured here, longest to shortest. Within IL, it ranks 1,235 of 1,548.
Learn more
local microclimates explains what one yard in Winnebago can differ from the 61105 normal, and zone vs. frost date explains why Zone 5b and Winnebago's frost date answer different questions.