Something called the 'Ekman Spiral' has driven the big lake's surface water to a bone chilling 45 degrees in some spots.

While the weekend air temperatures look like they would be perfect for swimming, be careful at the Lake Michigan shore, as surface water temperatures continue to drop following this week's autumn-like winds.

Days of winds from the north have pushed the warmer water to the west, replacing it with deeper, coder water along the shore, a phenomenon the National Weather Service calls the Ekman Spiral.

Surface water temps are coldest along Lake Michigan from Muskegon to Pentwater, bottoming out at around 45 degrees. While more southern beaches have slightly warmer water, it's still going to be a chilly dip if you head to the lake this weekend.

Cold water is no joke, the NWS reminds you that just a few minutes in below 50 degree water can incapacitate the average person.

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