Does Lake Michigan have any tides?
— Frank Stoil, Door County, Wis.
The U.S. National Ocean Service says Lake Michigan and the other Great Lakes are “essentially non-tidal” because their very small tidal fluctuations are masked by much larger fluctuations of lake levels produced by changes in wind and air pressure. In reality, the Great Lakes, like all bodies of water, experience tides that are caused by the gravitational pull of the sun and moon. Measurements indicate twice-daily tidal fluctuations of 0.5 to 1.5 inches on Lake Michigan. However, Dr. Dave Schwab of the Great Lakes Environmental Research Lab in Ann Arbor, Michigan, notes the existence of a larger Lake Michigan tidal swing in the Bay of Green Bay, where local geography can generate a 4-inch tide.