St. Martin, MN 56397 Frost Dates
Frost dates for St. Martin, MN, ZIP 56397
The last spring frost here typically falls around 05/03, about 248 days from today. The first fall frost typically arrives around 10/07, about 155 frost-free days later.
Zone 4b (-25 to -20°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 St. Martin, not a forecast for this year.
What to do before the first frost
Zone 4b around St. Martin has about 6 weeks left before the first fall frost — that's the usual window to get a cold frame up if you want to keep harvesting past it.
The actual range around St. Martin's last frost
05/03 is the middle of 30 years of NOAA records, not a promise. Plant by 04/21 and you're betting against frost in roughly 9 years out of 10. 05/17 is the safer bet, historically only a 1-in-10 chance of frost that late.
How St. Martin compares
About 155 days separate St. Martin's last and first frost, putting it 34,128 of 40,283 ZIP codes nationally. Within MN, it ranks 371 of 943.
Learn more
zone vs. frost date explains why Zone 4b and St. Martin's frost date answer different questions, and the frost range explains how to read the range around St. Martin's dates instead of trusting one.