While the water hasn’t warmed to comfortable swimming levels yet, each Great Lake is surprisingly warmer than the long-term average water temperature for this date.
May has had a dual personality as far as temperatures go. The first half of May was significantly colder than normal, while the second half has been warmer than normal. But what’s interesting is you see in the graphs below that the Great Lakes each have been warmer than normal for quite a few months.
Lake Superior is warmer than average, but still too cold to enter, with water temperatures still in the upper 30s and lower 40s.
Surface water temperatures on Lake Superior on May 27, 2021
Lake Superior's average surface water temperature this year(red) versus the long-term average(blue)
The southern end of Lake Michigan and Saginaw Bay on Lake Huron are really starting to warm up. It looks like the eastern part of Saginaw Bay may be warmed up to 68 degrees.
Surface water temperatures on Lake Michigan and Lake Huron on May 27, 2021
Lake Michigan is about four degrees warmer than average, and has been warmer than average all year.
Lake Michigan average surface water temperature this year(red line) versus the long-term average(blue line)
Lake Huron average surface water temperature this year(red line) versus the long-term average(blue line)
Lake Erie has warmed into the lower 70s over the shallow, warmer west end of the lake.
Surface water temperatures on Lake Erie on May 27, 2021
The graph below shows the lake-wide average water temperature for Lake Erie is about seven degrees warmer than normal.
Lake Erie average surface water temperature this year(red line) versus the long-term average(blue line)
Finally we look at Lake Ontario, which is a deep lake and normally quite cold. While Lake Ontario is still way too cold to swim in, it is substantially warmer than usual for this date.
Surface water temperatures on Lake Ontario on May 27, 2021
The graph of Lake Ontario’s average surface water temperature shows the water temperature is usually around 42 degrees for May 28. But this year the lake has already warmed to an average temperature around 56 degrees. Lake Ontario is 14 degrees warmer than normal.
Lake Ontario average surface water temperature this year(red line) versus the long-term average(blue line)
It’s interesting that even in a stretch of colder than normal weather in late March, April and the first half of May, Great Lakes water temperatures didn’t drop below normal.