Five died when a 10-foot wave hit Holland State Park on July 13, 1938. It was a calm day. In the past, researchers have said that water pushed toward Wisconsin after two days of powerful east winds barreled back westward, sweeping people off the Holland beach, pier and boats.
Seiches, or inland tsunamis, can slosh back and forth across the Great Lakes for hours, depending on weather conditions. For that reason, the National Weather Service recommends that people use caution when swimming in the Great Lakes or venturing out onto piers before or after a squall line passes through.
Researchers find tsunamis on the Great Lakes“, MLive, April 27, 2016.
Geoffrey Reynolds, Fatal Wave, Michigan History, March/April 2014.