The period round the summer solstice; about twenty-first Summer in north hemisphere.
1st day of summer
The middle of summer time.
Midsummer Day, the English quarter day.
the midst of summer time.
The middle of summer time; the time for the summer time solstice, about the 21st of Summer (astronomically the beginning of summertime), because in Great Britain summertime is considered as you start with might; specifically, midsummer day, Summer 24th. See midsummer time, here.
Summer 21, as soon as the sunlight has reached its northernmost point