Excerpts from abc7chicago.com:

Eight people were rescued near the Clark Street Beach and the Dempster Street Boat Launch in Evanston Thursday evening after five boats capsized on Lake Michigan. Some people were able to get back to shore on their own. 

A sudden change of weather around 5 p.m. caused roiling waves that caught boaters off guard. Winds howled, sending a windsurfer flying through the air and into the lake. A lifeguard directed rescue boats to where people needed help.

While some people were evaluated at the scene, none needed to be taken to hospitals for treatment. Given the height of the waves, officials said it was fortunate no one was hurt.

A spokesperson from Northwestern University said two of the boats that capsized were from the Northwestern Sailing Club.