Hermantown, MN 55811 Frost Dates
Frost dates for Hermantown, MN, ZIP 55811
The last spring frost here typically falls around 05/13, about 258 days from today. The first fall frost typically arrives around 10/01, about 140 frost-free days later.
The USDA Plant Hardiness Zone Map puts Hermantown in Zone 4b (-25 to -20°F average annual minimum); frost dates are NOAA's 1991-2020 station normal, not this year's forecast.
What to do before the first frost
Zone 4b around Hermantown has about 5 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.
Why 05/13 isn't a guarantee
05/13 is the middle of 30 years of NOAA records, not a promise. Plant by 04/29 and you're betting against frost in roughly 9 years out of 10. 05/29 is the safer bet, historically only a 1-in-10 chance of frost that late.
How Hermantown compares
About 140 days separate Hermantown's last and first frost, putting it 37,037 of 40,283 ZIP codes nationally. Within MN, it ranks 737 of 943.
Learn more
local microclimates explains what one yard in Hermantown can differ from the 55811 normal, and zone vs. frost date explains why Zone 4b and Hermantown's frost date answer different questions.