What causes powerful storms and large waves on the Great Lakes?

Severe storms on the Great Lakes are most frequent during late fall and early winter. These weather events are driven by strong winds that can reach gale force, which in turn generate large waves often exceeding 10 feet in height.1

The formation of these waves is a result of energy transfer from the wind to the water surface through frictional drag and direct force on the upwind face of the waves. The height of these waves is determined by the speed and duration of the wind, as well as the distance over which the wind blows, known as the fetch. In large bodies of water like the Great Lakes, where fetch is significant, waves can grow quite large, though they generally do not exceed approximately 7 meters (23 feet).2

Additionally, atmospheric disturbances such as winds or differences in barometric pressure can trigger seiches—harmonic oscillations that cause water to pile up temporarily on one side of a lake.1