Basic fronts will get the fish active. Sunfish will feed more during the fall as a rule. They need calories to survive and they are trying to eat all they can while bugs and minnows are still easy to get and before the winter sets in. The afternoon bite is better than the morning bite after several light fronts have passed. Once this arctic front passes sunnies will start to move to deeper water and will usually stay close to deeper water next to brush piles and ledges. Shallow water fish will be harder to find.
As for the Rios they to will become harder to find after an arctic front blows through.
Sunfish will stay active during the warmer times of the day and the big ones are usually easier to catch. Once winter sets in the bite slows down. You can still catch them in deeper water holding by brush piles.
Slow retrieves with plenty of patients is the winter game plan!