DOWNTOWN — Sunny skies and 80-degree temperatures might have you feeling beach-ready this weekend, but Lake Michigan is anything but fun for swimmers right now.

Beach season for the Chicago Park District kicked off on May 24 and the weather has finally heated up, hitting the 80s on Thursday. But after a long, slow start to the warm weather this year, Lake Michigan water remains particularly chilly. People face serious safety risks, including death, if they try to swim in the lake.

The water temperature around Chicago’s lakefront was just 64 degrees on Thursday, about 20 degrees colder than the day’s air temperature, according to Amy Seeley, a National Weather Service meteorologist. Another meteorologist, Paul Walker from AccuWeather, said the lakefront’s water was an even chillier 59 degrees by their measurement.

That’s significantly colder than the water temperature of 70 degrees recorded on the same day last year.

If you try to take a dip, you’ll feel the difference: There’s no one temperature considered safe for swimming, but several resources suggest 70 is the absolute chilliest open water should be for a swim.

The National Weather Service warns “survival time is greatly diminished for someone immersed in water below 70 degrees.” Cold water can cause swimmers to immediately lose control of their breathing and to gradually lose muscle control and body heat, which can be “immediately life-threatening.”

In fact, about 20 percent of people who fall into cold water will die in the first minute due to cold water shock and the loss of their breathing control, according to the National Weather Service.

Even those who survive the initial immersion may face health risks from hypothermia. Body heat is lost much quicker in cold water than in cold air, according to the National Weather Service.

How much cold water someone can handle varies from individual to individual, Walker said, with people’s body types playing a significant role in how long they’ll last.

“Different people react differently in cold water,” Walker said. “The concern with swimming in cold water is your core body temperature drops … .”

The National Weather Service advises those going near cold water to don protective gear like a life jacket and a wet or dry suit.

There are a lot of factors going into why Chicago’s lakefront waters are unusually chilly, Walker said. Rain, air temperature and wind direction all play a role.

Chicago’s had the usual amount of rain for this point of June, but it has been about 2.1 degrees cooler than normal, Walker said. In comparison, last June was about 3.9 degrees warmer than normal.

“I think air temperature’s playing a big role in this,” Walker said. “And the cloudy days and everything.”

It’s “complicated” to determine when the lake will warm up enough to be safe for swimming since so many factors are at play, Walker said.

But the National Weather Service is predicting air temperatures will hit 90 degrees Friday and stick to the high 80s throughout the weekend.

Those looking to keep track of the water temperature at local beaches can check the Chicago Park District site.

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