Winthrop Harbor, IL 53101 Frost Dates
Winthrop Harbor, IL: when does the frost end?
Typically, the last spring freeze lands around 04/19, roughly 234 days out. Fall's first freeze usually shows up around 10/26, roughly 189 days after the last spring frost.
The USDA Plant Hardiness Zone Map puts Winthrop Harbor in Zone 5b (-15 to -10°F average annual minimum); frost dates are NOAA's 1991-2020 station normal, not this year's forecast.
Stretching the season past the first frost
With roughly 8 weeks until Winthrop Harbor's first fall frost, a row cover or cold frame is what stretches the last few weeks of harvest here.
Why 04/19 isn't a guarantee
04/19 is the middle of 30 years of NOAA records, not a promise. Getting tender plants in by 04/06 carries real risk, frost has hit that late in about 9 of 10 years here. Wait until 05/03 and only about 1 year in 10 sees frost after that.
Winthrop Harbor against the rest of the dataset
Winthrop Harbor's growing season runs about 189 days, ranking 21,519 of 40,283 US ZIP codes measured here, longest to shortest. Within IL, it ranks 581 of 1,548.
Learn more
Before leaning on 53101's figures: local microclimates explains what one yard in Winthrop Harbor can differ from the 53101 normal, while zone vs. frost date explains why Zone 5b and Winthrop Harbor's frost date answer different questions.