Great Lakes water temperatures start to decrease early

Erin Sloan
Traverse City Record-Eagle

Traverse City — Great Lakes water temperatures may have started their yearly decline ahead of schedule.

George Leshkevich, a research scientist at the Great Lakes Environmental Research Laboratory, said each of the lakes is cooler than it was at this time a year ago.

“It seems like they’re cooling. The cooling usually starts in September,” he said. “But, in just seeing the forecast for northern Michigan in the last week or so, night temperatures and frost risks will affect the water temperatures.”

Lake Michigan seems to have been the least impacted, being only about 1 degree lower than last year, from 72 degrees to only about 71. Lake Superior was about 66 degrees last year and about 63 degrees this year.

Normal air temperatures in late August and early September usually land in the mid-70s, said Matt Gillen, a meteorologist at the National Weather Service in Gaylord.

“In 2016, we were still in the low 80s, about 84 degrees which is about 5-7 degrees above normal for this time,” Gillen said.

Leshkevich found it odd the lakes were already cooling, as in previous years the temperatures would remain fairly steady into mid-September.

“At this point though, it could still bounce back if we had some very hot, warm weather,” he said. “But we would need at least a week or two of warm at this point to have an effect.”

But Gillen said that’s likely not going to happen.

“There’s no signs of a substantial warm-up — that’s for sure,” he said.

The Great Lakes didn’t freeze much at all in winter 2016-17, meaning the lakes had a jump-start on getting temperatures high and keeping them high, Leshkevich said.

“Winter wasn’t that bad, there wasn’t that much ice cover meaning heating season would last longer,” he said. “In 2014 the opposite happened — we had a hard winter where the lakes froze and they weren’t able to absorb as much energy because the ice was there longer.”

Leshkevich said he wasn’t sure what this will mean for the next season, other than it potentially shortening water recreation time on the Great Lakes, but circled back to air temperature as the likely culprit.