Generally speaking it is a bad idea to water any plants during the hottest part of the day. You can "burn" the plant because of the way the sunlight is reflected through the water droplets.

To avoid this, it is advised that you water either very early in the morning or later on in the evening when the sun is about an hour away from setting. This will help you avoid "burning" your grass or any other plants. It is ineffective since quite a bit of the water can evaporate during the heat of the day.



Yes, it is bad for a number of reasons. First, the water tends to evaporate faster at the heat of the day, so the grass doesn't get the best benefit of watering. In my experience, the best time was once the heat of the day was over, so that the grass could recover from the stress and have some hours for the water to dry (in Houston, the concern is mold/fungus when watering over night). As mentioned above, the "burning" effect of water is also true. I preferred to do the slow drip in areas of the yard, moving the hose when the area was saturated, rather than using a sprinkler.