Iron Mountain, MI 49801 Frost Dates
When can you plant in Iron Mountain, MI?
Around 05/17 is the usual last spring frost, about 262 days away. The first fall frost typically arrives around 10/01, about 135 frost-free days later.
Iron Mountain sits in USDA Zone 4b (-25 to -20°F average annual minimum). The dates above are NOAA's 1991-2020 normal at the nearest reporting station, a 30-year average, not a forecast.
What to do before the first frost
About 5 weeks of growing season left in Iron Mountain before the first fall frost — a cold frame or row cover can stretch harvest weeks past that date.
The actual range around Iron Mountain's last frost
05/17 is the middle of 30 years of NOAA records, not a promise. Plant by 05/02 and you're betting against frost in roughly 9 years out of 10. 05/31 is the safer bet, historically only a 1-in-10 chance of frost that late.
How Iron Mountain compares
At roughly 135 frost-free days, Iron Mountain places 37,839 of 40,283 ZIP codes in this dataset. Within MI, it ranks 961 of 1,153.
Learn more
the frost range covers how to read the range around Iron Mountain's dates instead of trusting one. local microclimates covers what one yard in Iron Mountain can differ from the 49801 normal.