I have lived here since 1997 and ride the canal path often. During Sept. you can expect anything from 50 degrees to 80 degrees. It often starts off cool then warms as the day progresses. The trees may be beginning to turn by then.
One good thing, the Geese will not be nearly so aggressive. Their hatchlings are growing now. In spring and early summer they can be very aggressive and spend a lot of time on the path.
The path from Long Pond road on the west side of Rochester to about Fairport on the east side is paved, nearly 15 miles long. The ride through Genesee Valley park is quite nice. You actually cross the canal and Genesee River in the park. The path on either end of this stretch is mostly hard packed gravel. The ride is generally very easy with long flat stretches.
There is easy access at most road crossings. There are many town parks along the way as well. To see some locks in the Rochester area you would need to ride in the towns of Henrietta, Brighton or Macedon. The operation of the locks is quite impressive. Locks 32 and 33 are about 1 mile apart in Henrietta and Brighton. I believe they each drop the canal level approx. 25 feet.
There are many draw bridges over the canal, and there operation is fun to see if you time it when a boat is passing.
Overall this is an excellent adventure with plenty of beautiful scenery to see. There have been many hearty souls that have spent several days riding the entire length of the canal path.
Here are a couple of pictures directly across from Red Rock Ponds RV Resort. The yellow sign in the distance is looking east, the other is looking west (the sign is pointing to the entrance to the RV Park)