Ironwood, MI 49938 Frost Dates
When can you plant in Ironwood, MI?
Typically, the last spring freeze lands around 05/19, roughly 264 days out. The first fall frost typically arrives around 09/28, about 130 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 Ironwood, not a forecast for this year.
What to do before the first frost
About 4 weeks of growing season left in Ironwood before the first fall frost — a cold frame or row cover can stretch harvest weeks past that date.
The actual range around Ironwood's last frost
05/19 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. 06/03 is the safer bet, historically only a 1-in-10 chance of frost that late.
How Ironwood compares
At roughly 130 frost-free days, Ironwood places 38,369 of 40,283 ZIP codes in this dataset. Within MI, it ranks 1,027 of 1,153.
Learn more
local microclimates covers what one yard in Ironwood can differ from the 49938 normal. zone vs. frost date covers why Zone 4b and Ironwood's frost date answer different questions.