The buses are running and kids have returned to school. Many call this the end of summer. Others push the end of summer to the Labor Day holiday, which falls on September 3rd this year. From an astronomical standpoint, summer ends and fall begins with the autumnal equinox, when day and night are roughly the same length. This year the equinox falls on September 22, still a long way away. From a practical point, we tend to divide the months into 4 seasons, each 3 months long, with summer being June through August.
Mary Knapp, Weather Data Library