Marietta, IL 61459 Frost Dates
61459, near Marietta, IL: the frost window
The last spring frost here typically falls around 04/17, about 232 days from today. Fall's first freeze usually shows up around 10/22, roughly 185 days after the last spring frost.
Zone 6a (-10 to -5°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 Marietta, not a forecast for this year.
Stretching the season past the first frost
Marietta'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
04/17 is the middle of 30 years of NOAA records, not a promise. Getting tender plants in by 04/04 carries real risk, frost has hit that late in about 9 of 10 years here. Wait until 05/02 and only about 1 year in 10 sees frost after that.
Marietta against the rest of the dataset
At roughly 185 frost-free days, Marietta places 23,356 of 40,283 ZIP codes in this dataset. Within IL, it ranks 856 of 1,548.
Learn more
Two guides worth reading on 61459: local microclimates, on what one yard in Marietta can differ from the 61459 normal, and zone vs. frost date, on why Zone 6a and Marietta's frost date answer different questions.