Not an expert by any means...
But the way I understand it, and our lakes up here probably "flip" more than your lakes, is...
During the warm weather, the top layer of the lake is warm and the bottom layer is cold. But when the seasons change, the top layer becomes cold and the water underneath is warmer. Cold water is heavier than warm water. So when the top layer becomes colder than the bottom layer when the seasons change, the cold water sinks and the warm water rises...flipping the lake. Messes with temps and oxygen. Fishing is usually slow during this period.