Harrisburg, IL 62946 Frost Dates
62946, near Harrisburg, IL: the frost window
Typically, the last spring freeze lands around 04/19, roughly 234 days out. Fall's first freeze usually shows up around 10/20, roughly 181 days after the last spring frost.
Harrisburg sits in USDA Zone 7a (0 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
Harrisburg's growing season runs out in roughly 8 weeks — a cold frame or greenhouse kit is the usual way to keep cool-weather crops going past the first frost.
How much risk comes with planting early here
04/19 is the middle of 30 years of NOAA records, not a promise. Getting tender plants in by 04/03 carries real risk, frost has hit that late in about 9 of 10 years here. Wait until 05/08 and only about 1 year in 10 sees frost after that.
Harrisburg against the rest of the dataset
About 181 days separate Harrisburg's last and first frost, putting it 24,489 of 40,283 ZIP codes nationally. Within IL, it ranks 915 of 1,548.
Learn more
Two guides worth reading on 62946: local microclimates, on what one yard in Harrisburg can differ from the 62946 normal, and zone vs. frost date, on why Zone 7a and Harrisburg's frost date answer different questions.