Ironton, MN 56455 Frost Dates
56455, near Ironton, MN: the frost window
Around 05/13 is the usual last spring frost, about 258 days away. Fall's first freeze usually shows up around 09/27, roughly 138 days after the last spring frost.
Ironton sits in USDA Zone 4a (-30 to -25°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
Ironton's growing season runs out in roughly 4 weeks — a cold frame or greenhouse kit is the usual way to keep cool-weather crops going past the first frost.
The actual range around Ironton's last frost
05/13 is the middle of 30 years of NOAA records, not a promise. Getting tender plants in by 04/29 carries real risk, frost has hit that late in about 9 of 10 years here. Wait until 05/27 and only about 1 year in 10 sees frost after that.
Ironton against the rest of the dataset
Ironton's growing season runs about 138 days, ranking 37,443 of 40,283 US ZIP codes measured here, longest to shortest. Within MN, it ranks 771 of 943.
Learn more
Two guides worth reading on 56455: zone vs. frost date, on why Zone 4a and Ironton's frost date answer different questions, and the frost range, on how to read the range around Ironton's dates instead of trusting one.