someone told my son you can't get the leaves wet. They are in a hanging basket and was told only to water from the top and not wet the leaves and to bring inside when it rains. I told him they were nuts but he said that is what he was told when he bought them. HELP!!!
Petunias are, not at all, picky. They will tolerate just about any range of conditions, and thrive just fine. Wetting the leaves will not harm them, and they will do much better outside in the rain, then watering with tap water anyways. I know that many places will state that getting leaves and flowers wet will harm them, but this is really more for hot and humid climates. These conditions paired with wet leaves will cause mold and other viruses. In most areas, the rain will not harm them. Your area is cool enough. This would really apply if you lived in a place like Texas. Even in Tennessee it is not hot and humid enough to be of much concern. This article will help: https://www.gardeningknowhow.com/ornamental/flowers/petunia/petunia-container-care.htm