Can seasonal affective disorder begin as early as late summer (late aug- midsep)? i've read it is mainly a late fall/winter occurrence.

Seasonal Affective: Disorder can begin in late summer on a psychological level. One can begin to have anticipatory anxiety/depression thinking about the darker days ahead. All the more reason to live in the present moment and celebrate what you have now. See a book called "The Power of Now" by Ekert Tolle.

SAD: SAD is now referred to as Depressive Disorder with Seasonal Pattern in DSM 5. It is a subtype of depression. There are some people who develop seasonal affective disorder (SAD) in the spring or early summer. However, the majority of people experience SAD during the fall or winter. I am not aware of a pattern that begins in late summer.