We can usually expect Great Lakes’ water temperatures to mimic the summer air temperatures. This is mostly true this summer, except for Lake Superior.

The following graphs show this year’s average water temperature on each Great Lake. Lakes Michigan, Huron, Erie and Ontario all are amazingly close to the long-term average water temperature. Usually some part of the year has temperatures deviating significantly from the normal. The big deviation from normal really hasn’t happened this year on those four lakes.

Lake Michigan's water temperature this year (red) versus the long-term average (blue)

Lake Huron's average water temperature this year (red) versus long-term average (blue)

Lake Michigan's water temperature this year (red) versus the long-term average (blue)

Lake Michigan's water temperature this year (red) versus the long-term average (blue)

Water temperatures usually mimic what a few months of surface ground temperatures have averaged. If June and July have near normal temperatures, the Great Lakes waters usually track near normal.

So it’s no surprise that summer temperatures so far are just a few tenths of a degree warmer than normal.

But that is not the case for Lake Superior. Lake Superior became cooler than normal in early February and has stayed there since. Why? The answer is extremely cold temperatures for January, February, March and April. By extremely cold, I mean a significant deviation from normal temperatures.

Using Marquette as an example, January 2022 was almost six degrees colder than average. February was four degrees colder than normal. March was almost two degrees colder and April was three degrees colder than normal. Four months in a row seriously cooled down the biggest Great Lake. May being three degrees warmer than normal, June two degrees and July slightly warmer haven’t warmed Lake Superior to near normal.

Lake Michigan's water temperature this year (red) versus the long-term average (blue)

The next two weeks will be very interesting to watch Great Lakes’ water temperatures. We have some hot days on the way. We should see Lake Michigan, in the heart of the heat, warm dramatically. Lake Superior should warm a lot and maybe get to near average water temperatures. Lakes Huron, Erie and Ontario will be just outside the extreme heat, but still warm above normal.

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