The National Weather Service on Sunday issued a rip current warning along both the Illinois and Indiana shores of Lake Michigan.
Rip currents, powerful channels of water occurring most often at low spots or breaks in a sandbar, are likely through Wednesday morning, according to the weather service.
Swimmers are urged to pay attention to lifeguards, posted signs and flags warning of the currents.
If caught in a rip current, swimmers should remain calm and swim parallel to shore. Once you are away from the current's force, begin swimming toward the beach.
"Do not attempt to swim directly against a rip current," the National Weather Service said in a statement. "Even a strong swimmer can become exhausted quickly."
The Labor Day holiday marks one of the biggest swimming weekends of the summer.
After a hot, humid start to the month, Sunday temperatures grew more comfortable thanks to breezy northwest winds. Highs are predicted to reach 72 and dip to 56 overnight.
Temperatures dip further on Labor Day, with a high of 67 expected.