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Weather Blog: Lake Michigan continues to cool

Lake Michigan holds stories and mysteries
Posted at 10:05 AM, Oct 07, 2020

WISCONSIN — This summer Lake Michigan water temperatures climbed above average, warming into the mid 70s in early July.

Lake temperatures remained above average through much of the summer, but cooling quickly set in during September.

A few rounds of cooler weather, and an increase in winds, brought a halt to the warming. The winds promote mixing of the water, allowing the cooler subsurface water to rise to the top.

Now, the average lake temperature has dropped below 60-degrees. But that is an average, and it's a big lake! If we look more specifically at the water temperatures offshore from Southeast Wisconsin, it's even cooler.

On October 6th, the surface temperature reading just offshore from Milwaukee was only 46.2°F!

Over the summer, the lake helps keep coastal locations a bit warmer at night, thanks to the influence of the warm lake waters. However, the tables will turn shortly, and the lake influence won't moderate temperatures to a significant degree. Also, as we get days with east and northeast winds, coastal areas will turn considerably cooler, due to the cooler water temperatures.

A lake breeze is expected for late Thursday afternoon, which will likely drop temperatures near the lake from highs in the mid 60s, down into the 50s.

Note the area circled in red, the lake breeze impact is noted by the slightly cooler temperatures for coastal areas as winds turn onshore.

Looks like swim season is over. Until next year!

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