Mackinac Island, MI 49745 Frost Dates
When can you plant in Mackinac Island, MI?
Typically, the last spring freeze lands around 06/01, roughly 277 days out. The first fall frost typically arrives around 09/21, about 110 frost-free days later.
Zone 5a (-20 to -15°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 Mackinac Island, not a forecast for this year.
What to do before the first frost
About 3 weeks of growing season left in Mackinac Island before the first fall frost — a cold frame or row cover can stretch harvest weeks past that date.
How much risk comes with planting early here
06/01 is the middle of 30 years of NOAA records, not a promise. Plant by 05/18 and you're betting against frost in roughly 9 years out of 10. 06/20 is the safer bet, historically only a 1-in-10 chance of frost that late.
How Mackinac Island compares
About 110 days separate Mackinac Island's last and first frost, putting it 39,511 of 40,283 ZIP codes nationally. Within MI, it ranks 1,131 of 1,153.
Learn more
local microclimates covers what one yard in Mackinac Island can differ from the 49745 normal. zone vs. frost date covers why Zone 5a and Mackinac Island's frost date answer different questions.