Mackinac Island, MI 49719 Frost Dates
Mackinac Island, MI: when does the frost end?
Typically, the last spring freeze lands around 05/31, roughly 276 days out. Fall's first freeze usually shows up around 09/25, roughly 116 days after the last spring frost.
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.
Stretching the season past the first frost
With roughly 4 weeks until Mackinac Island's first fall frost, a row cover or cold frame is what stretches the last few weeks of harvest here.
The actual range around Mackinac Island's last frost
05/31 is the middle of 30 years of NOAA records, not a promise. Getting tender plants in by 05/14 carries real risk, frost has hit that late in about 9 of 10 years here. Wait until 06/14 and only about 1 year in 10 sees frost after that.
Mackinac Island against the rest of the dataset
Mackinac Island's growing season runs about 116 days, ranking 39,288 of 40,283 US ZIP codes measured here, longest to shortest. Within MI, it ranks 1,120 of 1,153.
Learn more
Before leaning on 49719's figures: the frost range explains how to read the range around Mackinac Island's dates instead of trusting one, while local microclimates explains what one yard in Mackinac Island can differ from the 49719 normal.