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Updraft® - Minnesota Weather News
Paul Huttner

Lake Superior finally nearing peak summer water temperatures

Record cold surface water in July has finally warmed up on the big lake.

A lifeguard looks at the beach near the end of Park Point in Duluth.
The beach at the city-owned beach house near the end of Park Point on Lake Superior.
Dan Kraker | MPR News

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Last month I posted about the record cold July water temperatures on Lake Superior.

You may recall water temperatures were still hovering in the upper 30s along the North Shore of Lake Superior in late July.

Lake Superior water temperatures in 2022
Lake Superior water temperatures in 2022.
Jay Austin UMD Large Lakes Observatory

You could see the ribbon of blue (frigid water) that hugged the shore late last month.

Lake Superior water temperatures
Lake Superior water temperatures.
NOAA/GLERL

Jay Austin from the University of Minnesota Large Lakes Observatory at the University of Minnesota Duluth wrote this last month.

Hi Paul-

Just heard your piece on inland lake temps. Lake Superior is an interesting story this year WRT temperature as well.

The western buoy site (NDBC 45006) only this week reached 39F, the latest it has done so in the last 42 years (the instrumental record); the other two sites (central (45001) and eastern (45004) Superior) have yet to reach the temperature where the lake can start to form a layer of warm water (39F).

This point is being reached about a month later than it does on average. The western site is 25F colder right now than it was at this time last year! This is due in part to the fact that we had a relatively icy winter; what intrigues me is that this winter was nowhere near as severe as 2013-2014, but the overturn date this year will be later than it was in 2014.

Jay-

Warmer water now

Warming the big lake has been a slow process this year. Jay reports that it took Lake Superior 3 months to warm 5 degrees from 33 to 39F, then only 3 weeks to warm 16 degrees from 39 to 55F.

Fast-forward to late August. Water temperatures along the North Shore have warmed into the 60s to around 70 degrees in some areas. That’s still brisk for a swim, but water temperatures are now closer to the average peak summer temperatures in the mid to upper 60s.

Here are a couple of buoy readings as of Tuesday.

  • McQuade Harbor near shore 70.9 degrees

  • South of Grand Marais buoy 64.2 degrees

Lake Superior buoy water temperatures
Lake Superior buoy water temperatures.
University of Minnesota Duluth

Overall water temperatures on Superior are mostly in the 60s this week.

Lake Superior water temperatures
Lake Superior water temperatures.
NOAA/GLERL

That’s pretty close to the average for peak summer water temperatures which typically occur in late August.

Many people define safe swimming as water temperatures at or above 70 degrees. So if you’re brave, it’s just about warm enough for a brisk swim in Lake Superior this month.