Iron River, MI 49967 Frost Dates
Frost dates for Iron River, MI, ZIP 49967
Typically, the last spring freeze lands around 05/31, roughly 276 days out. The first fall frost typically arrives around 09/19, about 111 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 Iron River, not a forecast for this year.
What to do before the first frost
Zone 4b around Iron River has about 3 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 Iron River's last frost
05/31 is the middle of 30 years of NOAA records, not a promise. Plant by 05/16 and you're betting against frost in roughly 9 years out of 10. 06/13 is the safer bet, historically only a 1-in-10 chance of frost that late.
How Iron River compares
At roughly 111 frost-free days, Iron River places 39,455 of 40,283 ZIP codes in this dataset. Within MI, it ranks 1,126 of 1,153.
Learn more
the frost range explains how to read the range around Iron River's dates instead of trusting one, and local microclimates explains what one yard in Iron River can differ from the 49967 normal.