Police chased off swimmers at North Avenue Beach on Monday after four people were treated for heat exhaustion. (CBS)

Updated 5/30/2011 at 6:15 p.m.

CHICAGO (CBS) — Chicago police closed North Avenue Beach early Monday evening for safety concerns after four people were transported to the hospital for heat exhaustion.

The announcement about the safety-related closure came over the public-address system shortly after 6 p.m., CBS 2’s Mai Martinez reports. A firefighting crew sprayed crowds with a mist of water from a 2 1/2-inch hose as beach-goers made their way from the lakefront.

LISTEN: Newsradio 780’s Mary Frances Bragiel Reports



Several ambulances were called to the beach about 5:30 p.m. after several people began feeling sick on the beach, Fire Media Affairs Dir. Larry Langford said. “They started falling down and were lightheaded,” he said.

One of the transported patients, an 18-year-old man, was unresponsive and taken to Northwestern Memorial Hospital in critical condition, Langford said. Three others were in stable condition, and a few other people declined medical attention, he said.

“They just started throwing us all off the beach — literally,” beachgoer Jennifer Epley said after police sent everyone home. “The cops were walking up and down, saying, ‘You need to get out of the water.’”

Earlier Monday, at least six people who attended Memorial Day parades in the Joliet area were taken to hospitals, suffering from heat exhaustion.

The beach closure capped a day of temperatures hovering around the 90-degree mark during the Memorial Day holiday.

Chicagoans headed to lakefront beaches in droves to get some relief from the heat.

By noon, it was hard to find even a few feet of empty space on the sand.

“It’s like a relief. It’s really just a relief because you know being in the city it’s so cold all winter and we’re all just pent up, and we’re all just been waiting and obviously we all came out,” said Braden Turner.

Asked what it was like to get her feat in the sand on a sunny day at the beach, after a long Chicago winter, beachgoer Shannon Serva said, “It’s fabulous, and just to have your toes done so people can see it is great.”

Samantha Kuebler said she hadn’t been waiting for Monday’s weather as long as everyone else at the beach, “because I love the winter. … Even the winter we just had. It was the best. It snowed all the time.”

Of course, she was in the minority on Monday. Many said they’ve been dreaming of the sand, sun, and surf for months and nothing was going to keep them away.

For some, not even an injury would stop them from hitting the beach.

Eben Hamilton’s crutches couldn’t keep him away from the lakefront.

“It’s a beautiful day. Finally, it’s a beautiful day,” he said.

Everywhere you looked, people were enjoying it, including plenty of people who took a dip in the lake to beat the heat – even though the water was still very cold. According to the Chicago Park District, the water temperature at Chicago beaches was only 53 degrees on Monday.

The hottest Memorial Days in Chicago were recorded in 1942 and 1953 when the mercury hit 93 degrees, National Weather Service meteorologist Charles Mott said. But so far Monday, the Chicago area has only reached a high of 87 degrees at O’Hare International Airport, he said.

Still, there’s no denying it’s hot. The heat index, how the temperature actually feels, was recorded at 92 degrees at Midway Airport at 2 p.m., the weather service said.

Only eight of the past 138 Memorial Days in Chicago have had high temperatures at or above 90 degrees, the weather service said.

The last time the temperature rose above 90 degrees on Memorial Day was 2006, when the high hit 91 degrees, according to the weather service. Other years that broke the 90-degree mark include 1994, 1988, 1978, 1953, 1944, 1942 and 1895.

Monday will also bring winds of 10 to 20 miles per hour, gusting occasionally to 25 or 30 miles per hour, and lows in the mid- to lower-70s, according to the weather service.

Tuesday will reach a balmy 88 degrees and there’s a 60 percent of showers, the weather service said.

(The Sun-Times Media Wire contributed to this report.)