What in the world is meteorological Summer? There are two kinds of seasons - meteorological and astronomical. Meteorologists keep it simple. Meteorological Summer begins June 1st and ends August 31st. Not too surprisingly, September, October, and November are "meteorological fall", December through February are meteorological winter, and March through May are "meteorological spring".
So why the difference? It's basically for record-keeping purposes and keeps things simple.
By the way, if you're looking at the calendar the last day of astronomical Summer is September 23.
Fox 6 Chief Meteorologist