Marietta, MN 56257 Frost Dates
56257, near Marietta, MN: the frost window
Typically, the last spring freeze lands around 05/03, roughly 248 days out. Fall's first freeze usually shows up around 10/02, roughly 151 days after the last spring frost.
The USDA Plant Hardiness Zone Map puts Marietta in Zone 4b (-25 to -20°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
Marietta's growing season runs out in roughly 5 weeks — a cold frame or greenhouse kit is the usual way to keep cool-weather crops going past the first frost.
Why 05/03 isn't a guarantee
05/03 is the middle of 30 years of NOAA records, not a promise. Getting tender plants in by 04/21 carries real risk, frost has hit that late in about 9 of 10 years here. Wait until 05/15 and only about 1 year in 10 sees frost after that.
Marietta against the rest of the dataset
Marietta's growing season runs about 151 days, ranking 35,195 of 40,283 US ZIP codes measured here, longest to shortest. Within MN, it ranks 506 of 943.
Learn more
Two guides worth reading on 56257: the frost range, on how to read the range around Marietta's dates instead of trusting one, and local microclimates, on what one yard in Marietta can differ from the 56257 normal.