i have never tried fly fishing for catfish, but over the past couple weeks i have been catfishing on conventional gear (i know shoot me) using primarily cut shad as bait. been catching tons of 6- 10 pounders and the fish have all been holding next to sunken trees and horizontal logs/ brushpiles in less than 6 feet of water. The water was very warm, high 80's-low 90's, and the fish were still there though i had to put my baits RIGHT in front of their noses to get a reaction. warm water normally means that fish move around less especially during the middle of the day. just try and tailor your strategy to really picking apart the structure you are fishing to get the cats that are in there, but just no wanting to move far from where they are sitting.
best of luck to you!