Lake effect does not include just snowfall

The lake also has a significant affect on our weather during the late spring and summer, in addition to the lake effect snow that we experience during the winter. 

The heat retention of the water in Lake Ontario helps to cause lake effect snow, by creating instability when colder air crosses its surface.  Conversely in the late spring, the cooler water causes a placating effect on the air above it, making it more difficult for clouds to form, sometimes even inhibiting their formation.

This can be called a “lake shadow” or “Oasis Effect” and is visible from satellite images downwind from many of the Great Lakes in the late Spring.