NWS Great Lakes forecasts describe significant wave height—the average of the highest one-third of waves. Individual waves vary, and occasional waves can be higher than the headline value.
Period, direction, current, boat size, loading and course all affect how a forecast feels aboard. Short, steep Lake Erie waves can be uncomfortable even when the number appears modest.
Use the official forecast with current buoy observations, maintain conservative margins, and turn back when conditions exceed the vessel or crew’s capability.