I have 2 pots and 2 hanging baskets on my porch every year and they always do well, until this year. I bought new and replanted and they died.
What Happened to My Petunias This Year
Certified GKH Gardening Expert
It is possible that the soil became dried out. When this happens, some potting soils can actually start to repel water. You have to soak the pots underwater for 10 minutes or so to rehydrate the soil. I suspect that this may be what happened, which resulted in the plants not getting enough water and dying.