I started July 30th this year on my NOBO thru. Almost no bugs and resonable temperatures. Warm to almost hot in the southern part during the day. The low I encountered the northern section was 40F at "Puffer". The next few nights were also about the same since the capsites are all at higher elevations.
The only deterrent to this time frame is the "bubble" of AT hikers, both NOBO and SOBO in the joint southern 100 miles.