1. Everything is new. New jobs, new classes, new students, new books, new clothes, new shows on tv, new theater and symphony seasons. New muscular physiques and bulges to gawk at.
2. Everything is busy. The mind-numbing boredom of summer is replaced by days packed with activity. Every moment is vibrant and alive.
3. It gets crowded. The mind-numbing loneliness of summer is replaced by crowds of people, returning from their conferences, vacations, visits to relatives, and various excursions, ready to hang out with you again.
4. It gets cool, so you can jog a few miles without getting soaked.
6. Football. I don't like watching football, but I like watching football fans.
8. The trees change. After two decades in Los Angeles and Florida, where they didn't, it's quite a spectacle.
9. The days get shorter. The sun sets at a normal time, instead of that ungodly 8:00 or 9:00 pm.
10. The best holidays, Halloween and Thanksgiving. Not to mention my birthday.
12. Snow is coming soon.
See also: 10 Things I Hated About Summer and Playing Outside.