Lake Superior warming quickly this year

DULUTH – Lake Superior is warmer than average for this time of year, bringing swimmer-friendly temps to Duluth shores on what should be a blistering holiday weekend.

Surface temperatures on the western corner of the lake have reached the mid-60s — the water rarely warms above 70 degrees — much earlier than usual.

"We're finding ourselves a half-month to a month ahead of schedule," said Eric Anderson, a researcher with the Great Lakes Environmental Research Laboratory. "Because Superior is so big, and has so much cold water, that springtime warm-up usually takes much longer."

The lake as a whole recorded its fourth-warmest July 1 temperature since 1995, when satellites started tracking the average surface temperature of the Great Lakes, Anderson said.

The earlier warming this year follows a relatively mild winter and a hot and dry start to the summer. With little ice on Lake Superior, save for a short spike in February, water temperatures did not drop as much, which made for a faster warm-up this spring.

While that is great news for folks looking to cool off as temps near 90 around Duluth this weekend, it sets the stage for possible algae blooms later this summer.

On Thursday, the average lakewide temperature was 52 degrees, the warmest for the start of July since 2012 when Lake Superior hit record summer temperatures and saw its first documented algae bloom near the Apostle Islands.

Warm water and a major storm created ideal conditions for the potentially toxic green scum.

The water temperature near Duluth this week, about 64 degrees, is the same as it was toward the end of June in 2012.

"I think most people think of Lake Superior as enormous and pristine, but we're starting to feel the effects of a changing climate with the lake temperature rising," researcher Kaitlin Reinl said in a news release asking the public to report any algae blooms they spot by e-mailing DNRHABS@wisconsin.gov. "We have an opportunity to be proactive instead of reactive."

Average Lake Superior surface temperatures typically peak in the low 60s in mid-August.

The deepest parts of Lake Superior are almost always close to freezing, which means even as air temperatures rise the temperature of the water might quickly head the other direction.

"What makes Lake Superior so dangerous is this huge reservoir of water that's right around 40 degrees at the bottom of the lake, and significant wind events can bring that water up," said Jay Austin, a University of Minnesota Duluth professor and researcher at the Large Lakes Observatory. "People should be aware of the fact it might feel nice as you're getting in, but don't count on it staying warm."

Austin said it's a phenomenon that happens several times a summer on average, especially on the South Shore near the Apostle Islands but occasionally along Park Point as well.

"The wind can move water around, and how it does that is a little surprising," he said.

On Thursday, a rip current warning was issued for Duluth's Park Point as high winds churned up dangerous waves that authorities say swimmers should always avoid.

Visitors to the Park Point beach, the longest freshwater sandbar in the world, should watch for red and yellow flags that warn of rip currents and visit parkpointbeach.org to check conditions. Green flags mean rip currents are unlikely but not impossible.

"Rip currents can develop at any point in time," Duluth firefighter Ben Tessier said. "It's nice to get in the water and cool off, but first things first — when you're approaching the beach, check the flags. And if you're swimming with children, never take your eyes off them."

A 19-year-old woman was knocked down by a wave and unable to stand back up Thursday afternoon about 40 feet off Park Point beach, Duluth officials said. She was brought to a hospital after her friends were able to get her to shore.

Winds should calm down over the weekend. As for water temperatures in the lake for the next few days, Anderson said: "Things look pretty stable."

"Our models right now are showing a pretty nice July 4 weekend."

Brooks Johnson • 218-491-6496