While the Great Lakes have a profound effect on the weather across the region year-round, when "lake effect" is heard one is almost assured to think of snow. Lake effect showers in the form of rain often occur in the autumn when the first large, cool air masses spill southeast out of central Canada across the Great Lakes. However, lake effect rain showers in August are a very rare event.
Yet another indicator of just how unusual this summer has been occured Saturday evening and into the pre-dawn hours of Sunday when lake effect rain showers fell across the extreme southwest corner of lower Michigan and far northwest Indiana right up to the Illinois border.
A very sharp buckle in the jet stream southward across the upper midwest to the lower Mississippi valley, and then east across the deep South allowed a pocket of very cool air to drop across the Upper Great Lakes. This cool air flowing southward down the length of the warm Lake Michigan waters resulted in lake effect showers streaming in off the south end of the lake.
108 AM CDT SUN AUG 23