Hi Karrie ~
I agree wholeheartedly with loz ~ Portulacas might do very well for you!
The problem many people encounter with petunias throughout the middle United States is that they start looking way too shabby by mid-summer. The sun is just too much for them. So lots of folks I know in OH, KY, IN, etc., only use them as a spring flower
Here in Maine where the summers are more mild, petunias FLOURISH like crazy. When my OH family visits, they can't quite believe their eyes at the abundance of rich hardy blooms still going strong in August.