I am not an expert on petunias, but I have planted them in the past. It is my understanding that most of them with the exception of the wave petunias are really cool weather plants and stop blooming this time of year. I am not sure if they will bloom again in the fall or if the summer heat kills them.

It's not uncommon for petunias to look a little worn out after a rain. Just deadhead the blooms that have gotten beaten down and you'll probably have new blooms in a few days. Just as lisa455 said, petunias are more of a cool season plant in Louisiana, but they should make it until June before you need to replace them (North Louisiana). When they start getting really leggy, pinch them back about 1/3. They'll rebound really quickly.