Bring a coat, the temperature dropped and it's going to be brisk when you're here.
Ditto on what @johnmahlon said about the Warner Parks, they are past peak fall color but still worth the hike.
There are some really decent bike rides both within the city (Greenways, Music City Bikeway, etc) and just outside of it (Natchez Trace, Del Rio PIke, etc.), ping me if you ride and want to brave the weather.

