Summer

The season between spring and autumn comprising in the northern hemisphere usually the months of June, July, and August or as reckoned astronomically extending from the June solstice to the September equinox. – source...

Autumn

The season between summer and winter comprising in the northern hemisphere usually the months of September, October, and November or as reckoned astronomically extending from the September equinox to the December solstice —called also fall -source...