St. Martin, MN 56398 Frost Dates
56398, near St. Martin, MN: the frost window
Around 05/03 is the usual last spring frost, about 248 days away. Fall's first freeze usually shows up around 10/07, roughly 155 days after the last spring frost.
The USDA Plant Hardiness Zone Map puts St. Martin 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
St. Martin's growing season runs out in roughly 6 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 05/17 and only about 1 year in 10 sees frost after that.
St. Martin against the rest of the dataset
St. Martin's growing season runs about 155 days, ranking 34,129 of 40,283 US ZIP codes measured here, longest to shortest. Within MN, it ranks 372 of 943.
Learn more
Two guides worth reading on 56398: the frost range, on how to read the range around St. Martin's dates instead of trusting one, and local microclimates, on what one yard in St. Martin can differ from the 56398 normal.