Morton, IL 61550 Frost Dates
Morton, IL: when does the frost end?
Around 04/21 is the usual last spring frost, about 236 days away. Fall's first freeze usually shows up around 10/17, roughly 178 days after the last spring frost.
Morton 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.
Stretching the season past the first frost
With roughly 7 weeks until Morton's first fall frost, a row cover or cold frame is what stretches the last few weeks of harvest here.
Why 04/21 isn't a guarantee
04/21 is the middle of 30 years of NOAA records, not a promise. Getting tender plants in by 04/07 carries real risk, frost has hit that late in about 9 of 10 years here. Wait until 05/07 and only about 1 year in 10 sees frost after that.
Morton against the rest of the dataset
About 178 days separate Morton's last and first frost, putting it 25,593 of 40,283 ZIP codes nationally. Within IL, it ranks 1,075 of 1,548.
Learn more
Before leaning on 61550's figures: zone vs. frost date explains why Zone 6a and Morton's frost date answer different questions, while the frost range explains how to read the range around Morton's dates instead of trusting one.