It depends on you. You can water the lawn daily, once a week, or four times a month, shutting down the watering system during the rainy season because rain can provide just as sufficient water supply as necessary. The best time of the day to water the lawn is often in the morning hours. But if you prefer to do the same task in the evening, make sure you saturate the ground to a depth of at least 8 inches. Also read: What temperature is too hot to water grass