Lake Michigan’s lake effect on areas east of Chicago

Dear Tom,
Chicago gets an average of 35-40 inches of snow a year. How does that increase across northwest Indiana and southwest Michigan?
— Jeff Kozinski, Mokena

Dear Jeff,

Lake effect plays a major factor in annual snowfall totals in areas to the east of Chicago. While Lake Michigan does enhance snowfall totals to a degree on the Chicago side of the lake when winds are northeast, the increase is far more substantial across northwest Indiana and southwest Michigan, where arctic air frequently sweeps across the lake on persistent northwest winds.

Annual snowfall normals increase to 40 to 60 inches from the Gary area east to La Porte and to 60 to 70 inches around South Bend. Heading into Michigan, the effect is even more pronounced, and annual totals typically are in the 80-100 inch range.