serotinal

(sɪˈrɒt n l, ˌsɛr əˈtaɪn l, adjective) Serotinal is the most romantic and beautiful word pertaining to this time of year, alluding to or occurring in late summer. For example, the breezy, cool nights, the leaves on the ground, the earlier occurrence of the sunset and back to school season are all serotinal manifestations. They are the beginning markings of autumn in the form of summer nostalgia.  
(via wordsnquotes)