Though summer-like conditions continue Thursday in Chicago, a beach warning in effect through the day urges swimmers to stay out of Lake Michigan.
The National Weather Service reports 20 mph winds could churn up "pounding waves" as high as six feet along the lakefront in Illinois and northwest Indiana.
Strong rip currents and structural currents are expected as a result, creating dangerous swimming conditions.
This summer, officials said 20 people have drowned in Lake Michigan, including six in Chicago. Last year, authorities said seven people died after being pulled under by a rip current.
Rip currents are described as powerful channels of water flowing quickly away from shore, often occurring at low spots or breaks in sandbars. The currents can sweep swimmers from shore into deeper water.
The beach warning is expected to end late Thursday as the wind and waves die down.
Weather conditions for the day look partly to mostly cloudy with highs ranging from 70 degrees along the lake, mid-70s inland and upper 70s far southwest.
The rest of the week looks sunny and warm, but showers are on the way for the weekend.