it's not so much the amount of rainfall that matters, but how your soil reacts to and manages that rainfall that needs to be considered. As for rainfall, the state average is around 35 inches - plus or minus a few depending on your location
Marshall

You can't go wrong with sedums! Get sedum 'Autumn Joy', and after it's established, it will fluorish in the hottest weather and a lot of rain won't hurt it. It's almost impossible to kill.

And each year it will get a little bigger. After a few years, you can divide it. I bought one plant ~fifteen years ago, and now I have six large plants.

They bloom in late August/ early September.

Here is a link that might be useful:

A classic combo: purple coneflowers, black-eyed susans, daisies.