Well, answering one part of this question is easy. Almost every winter, ferry boat service from the mainland gets interrupted by ice in the Straits of Mackinac. So, how cold does the water around Mackinac Island get? Cold enough to freeze!
Of course, by the time the visitor season resumes in late April, the ice has melted and the water is warmer. But how warm is the water in the spring? And how much warmer does it get in the summer?
While water temperatures in any given year fluctuate depending on the weather, here’s a look at seasonal averages to give you an idea of whether you want to pack a swimsuit for your trip:
- By the time Opening Day of the visitor comes around at the start of May, the average surface water temperature off Mackinac Island is around 40 degrees. Brrrr!
Spring And Summer Water Temperatures On Mackinac Island
- The water warms and typically hits 50 degrees by Memorial Day, then steadily rises through June toward 60 degrees. Mackinac Island paddling trips with Great Turtle Kayak Tours and parasailing adventures with Mackinaw Parasailing usually begin for the season in May. Charter fishing trips off Mackinac Island and Mackinac Island boat cruises often start in May, too.
- The best months for swimming on Mackinac Island are July and August when water temperatures are well into the 60s and sometimes above 70 degrees. The annual Mackinac Island yacht races that start in Chicago and Port Huron, Mich. are held each summer in July.
Fall Water Temperatures on Mackinac Island
- The warm summer water around Mackinac Island often lingers past Labor Day under the clear, sunny skies of September. However, more surface heat escapes as the nights get cooler. While water temperatures in September can be in the high 60s and even reach 70 at times, they also can plunge down into the 50s as summer turns into fall. Guided paddling excursions, parasailing and Mackinac Island boat tours typically end for the season in mid- to late September.
- By October, fall colors on Mackinac Island are peaking and autumn is in full force, with air temperatures falling and water temps sinking back into the 50s
Winter Water Temperatures on Mackinac Island
- During the offseason on Mackinac Island, water temperatures gradually fall from the 40s in November to the 30s in December. They reach the freezing point around New Year’s Day when ice often starts to form. When the ice gets thick enough, winter ferry service gets suspended.
- February and March typically mark the low points for Mackinac Island water temperatures, with averages right around the freezing mark at 32 degrees. By late March, any remaining ice thaws and water temperatures begin increasing once again.
(CAUTION: SWIMMING ON MACKINAC ISLAND IS RECOMMENDED FOR EXPERIENCED SWIMMERS ONLY. WITH THE COOL TEMPS, BIG WAVES AND CHANGING CURRENTS, USE EXTREME CAUTION WHEN ATTEMPTING TO SWIM NEAR MACKINAC ISLAND.)
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