This is a gardening myth that refuses to die. Think about it. How often do plants get watered naturally by a passing shower, followed by exposure to bright sunshine? It happens all the time. Yet you don't see burned leaves in the garden. Watering during the sunniest part of the day will not sunburn your plants. In some cases it may even benefit the plants by cooling them off. Overhead sprinkling during the middle of the day is not the most efficient way to water. The wind is often stronger then than it is early in the morning, so you'll lose more water to evaporation, and some of the spray may be blown away from the plants you intend to water. It's best to water early in the day so that plants will dry off before evening. Foliage and flowers that remain wet for a long time are more likely to develop disease problems.