(I did not realize such the difference in northern lakes )

http://www.chicagotribune.com/news/l...525-story.html

Chicago's in for a hot weekend, but be warned before jumping in the lake — it's cold

Cold water swimming

Ashley Novoa finally gave in Friday after her son’s repeated requests to have a beach day.

She considered letting 3-year-old Jack Alison dip only his toes into Lake Michigan because she suspected the water hadn’t had a chance to warm up enough for swimming.

“I wanna go all the way in,” Jack said, holding his bucket of toys.

“He has other plans,” Novoa said as she laughed.

Her instincts were spot on.

Chicago Fire Department and National Weather Service officials warned swimmers to think before jumping into the lake Memorial Day weekend, the official start of beach season in Chicago. Lake Michigan’s water temperature near the Chicago shore was 57 degrees Friday. The water had warmed up 17 degrees since March 4, when Chicago Special Olympics held its Polar Plunge and the water was 40 degrees.

Ron Dorneker, deputy district chief for the Fire Department’s marine and dive unit, said the department wants to cut down the number of water rescues this year and urged the public to not be fooled by warm air temperatures.

The department last season responded to about 200 water rescue calls and pulled out an estimated 100 people from local waters. Swimming in cold water, generally any water below 70 degrees, is dangerous because it can cause hypothermia or cause someone to drown, Dorneker said.

“So water temperature in the 50s is going to zap your strength when you swim,” he said. “Think about when you go to a Chicago Park District pool; those pool temperatures are typically about 80 degrees. So we’re looking at a water temperature almost 25 degrees less than that.”

Jumping into cold water can cause a person to reflexively gasp, then get water in their lungs, according to the National Weather Service. Hypothermia typically happens when a person’s body temperature drops below 95 degrees.

But even in warmer water, how long someone stays in the water can factor into someone developing hypothermia, said Eric Anderson, a physical oceanographer with the National Oceanic and Atmospheric Administration.

It may be cold, but the lake near the Chicago shore is actually 3 degrees warmer than it was this time last year, Anderson said. And Friday’s water temperature was about the same as in 2016, he said.

How soon the lake warms depends on ice coverage, air temperatures and how many sunny days Chicago gets, Anderson said. And the water temperatures might vary depending on what side of Lake Michigan you are on, he said.

The lake’s temperature is even affected by the direction of the wind. Winds coming from the north and the east warm up the lake because they cause waves that send surface water that is typically warmer toward Chicago’s shoreline, Dorneker said. But winds traveling from the south and west blow warm surface water out and away from the city, bringing in water from the bottom of the lake that is colder, Dorneker said.

Heavy winds can cause water temperature to drop by 10 degrees within 10 to 12 hours, Dorneker said.

But even if the area gets winds from the north and the east this weekend, it will not do much to warm up the lake because the surface water isn’t as warm as during the months of July or August, Anderson said.

While the lake was expected to stay chilly, outside temperatures are a different story. On Friday, the high hit 88 degrees at O’Hare and Midway airports, with lakefront temperatures hitting 86, while the highs for Saturday and Sunday are expected to be in the 90s, according to the weather service. The forecast high for Memorial Day was 90 degrees.

If beachgoers can’t stifle the temptation to cool off in the water, they should make sure a lifeguard is present, Dorneker said. Parents should watch their children carefully, and those on boats should wear life jackets, he said.

By Friday morning, North Avenue Beach was starting to get crowded with people sunbathing, eating lunch and playing volleyball. Three men in waist-deep water tossed a Frisbee to each other. Des Plaines residents Arsalan Afshar, 18, and Kristian Dankov, 18, were meeting up with friends at the beach. Both had their swim trunks on and were going to take their chances taking a dip.

“You get used to it,” Dankov said. “Obviously, if you’re still shivering, it’s too cold.”

But other beachgoers like Jamie Rinaldi, 21, of Edison Park, had no plans to get in the water. She was at North Avenue for a photo shoot and also regularly does yoga at the beach.

“Definitely not today,” Rinaldi said about swimming in Lake Michigan. “It’s way too cold for that. In August or July? Yeah.”

emalagon@chicagotribune.com
Twitter @ElviaMalagon