Storms start to move out of Minnesota, continue for western Wisconsin

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Water temperatures in Minnesota’s inland lakes are balmy and near peak seasonal levels.

But the water in Lake Superior this summer is near record cold levels for late July. 

Water temperatures at buoys on the western end of the big lake are still a frigid 39 degrees this week. 

I got this note Friday from Jay Austin, with the 

Why is the North Shore so cold? Upwelling

So why is the western side of Lake Superior along the North Shore so cold right now? One reason is that persistent westerly winds have been pushing warmer surface waters away from shore. That causes colder water from the depths of the huge lake to rise along the North Shore. It’s a process called upwelling.

The Duluth NWS office has a good explainer.

But there may be more to it according to Jay Austin. And they are hoping to get more data next week from sensors in the lake. 

Inland lakes nearing seasonal peak warmth

Our spectacular Minnesota lakes offer us a welcome respite on hot summer days. Water temperatures on inland lakes are nearing seasonal peaks as we move into early August. Typically lakes around the Twin Cities peak at around 80 degrees in early August. 

 lake water temperatures reports from MPR Weather Twitter followers as of Friday, July 29. 

It should be noted that inland lake water temperatures in the top couple of feet are often significantly warmer than water 3-6 feet below the surface. Jumping into lakes, especially in northern Minnesota can be a bracing experience when you hit the water a few feet down as your body hits the thermocline region where water temperatures fall quickly with depth. 

I expect water temperatures will peak on many Minnesota lakes next week as our next heat event moves in.

Next week looks like it could challenge for the hottest week of summer overall. Minnesota will ride the northern end of an intense heat wave. 

Temperatures over 100 degrees are likely next week across Kansas, Nebraska, Iowa, and South Dakota. Bank thermometers in western Minnesota towns like Madison and Appleton could flash 100 degrees by next Tuesday.

The hottest day for the Twin Cities right now appears to be next Wednesday. Both the American GFS and European models have been cranking out highs between 96 and 99 for the Twin Cities next Wednesday. 

Paul Huttner

Author

Lake Superior water temperatures are still a frigid 39 degrees in many locations.

Lake Superior near Grand Marais in June 2022

Lake Superior near record cold for late July. Inland lakes nearing summer peak warmth.

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