Every lawn should be watered as early as possible, 4-7 am is ideal. If you have to water twice in one day, water a 2nd time 12 hours later. Watering in the afternoon, when the sun is at its strongest, could have the reverse effects. Wet grass could act as a prism for the beaming sunlight and make it easier for the sun to burn up your lawn.
Water leaches through the sand much faster than other soils. This requires less water than other soils to get the soil moist four inches down where the roots extend. Unfortunately, sandy soil dries quicker than other soils. Instead of increasing the time the lawn is watered, just water more frequent. When temperatures are in the 90’s and above, you may need to be watering twice a day, 15-20 minutes each zone. In cooler weather, water once a day for the same amount of time.