As I already said many times
Summer is the most light-blessed quarter of the year during which nature is in its prime and day greatly dominates night. Summer Solstice aka Midsummer is the middle point and pinnacle of Summer - if it were its beginning then Summer would merely be a Season of withering nature and intolerable heat.
In the second week of August, when Summer ends, nature assumes a withered appearance. Come September all the undeniable hallmarks of Autumn are already in place: night and day are equal lenght, the air is chilly, it rains all the time, leaves are losing their color and falling down in places, it's ogre. September seems totally pathetic if you think of it as a Summer month but magnificent when put in its proper place - the heart of Autumn.