Lake Erie has the strongest basin-to-basin water-temperature contrast among the Great Lakes because its western basin is extremely shallow while its eastern basin is much deeper.
The western basin averages only about 7 metres deep, whereas the eastern basin reaches roughly 64 metres at its deepest point. Shallow water responds quickly to sunlight, air temperature, and wind, while deeper water changes more slowly and can retain colder conditions below the surface.
The central basin lies between these regions and has intermediate characteristics. Seasonal winds can also move warm or cold surface water, so the contrast changes during the year rather than remaining fixed.
This basin structure affects ecology, navigation, ice formation, and algal blooms. Western Lake Erie, including the area near Toledo, is particularly vulnerable to nutrient-driven cyanobacterial blooms because shallow water and runoff can combine to support rapid growth.