The Lake Forest Fire Department responded around 2:44 p.m. to the Lake Forest Boat Launch for a call of a missing boater, fire officials said.
The missing boater, who was on a 15-foot sailboat, was reported missing by a family member to Lake Forest police after he failed to meet them at the boat launch Sunday afternoon.
Lake Forest fire officials said the missing person is a 43-year-old Lake Forest man, but did not release his identity.
Emergency crews launched a search for the missing boater, but the water search was halted for the evening around 5:30 p.m., fire officials said.
"The water conditions were challenging, with waves reaching 4 to 6 feet," a statement from fire officials read in part. "In response, Lake Forest command called the U.S. Coast Guard for additional support.
A Coast Guard helicopter has been assisting with the search.
Crews were expected to resume their search Monday morning.