Chicago, IL 60699 Frost Dates
60699, near Chicago, IL: the frost window
Typically, the last spring freeze lands around 04/11, roughly 226 days out. Fall's first freeze usually shows up around 10/31, roughly 201 days after the last spring frost.
Chicago sits in USDA Zone 6b (-5 to 0°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.
Stretching the season past the first frost
Chicago's growing season runs out in roughly 9 weeks — a cold frame or greenhouse kit is the usual way to keep cool-weather crops going past the first frost.
Why 04/11 isn't a guarantee
04/11 is the middle of 30 years of NOAA records, not a promise. Getting tender plants in by 03/30 carries real risk, frost has hit that late in about 9 of 10 years here. Wait until 04/27 and only about 1 year in 10 sees frost after that.
Chicago against the rest of the dataset
Chicago's growing season runs about 201 days, ranking 17,438 of 40,283 US ZIP codes measured here, longest to shortest. Within IL, it ranks 232 of 1,548.
Learn more
Two guides worth reading on 60699: local microclimates, on what one yard in Chicago can differ from the 60699 normal, and zone vs. frost date, on why Zone 6b and Chicago's frost date answer different questions.