Many people are not sure when to water their lawn. But don't wait until it turns brown. Inadequate watering puts your lawn under severe stress, which increases its susceptibility to insects and disease. Instead, develop a regimen for regular watering.
Water before the heat of the day, in the morning, even before sunrise. Watering early gives the water a chance to soak in rather than evaporating away. Plus, if there is some excess water that cannot be absorbed, it will have a chance to evaporate. Watering in the evening allows the water to soak in, but excess water will not evaporate and will foster fungal damage.
It is important to water deeply to encourage deep root growth. Light watering results in roots that stay near the surface, because that is where the water is. The shallow ground dries out quickly and so the lawn will need more frequent watering. The deeper soil remains moist longer and so the lawn is less likely to suffer during a drought. Shallow roots are also considered to be a likely cause of thatch. The soil should be moist about 3 to 4 inches deep.
Avoid over-watering; more people over-water than under-water. You may be one of the people who feel that if a little water is good, then a lot of water is even better. That is not true. The objective is to provide enough water so that the lawn does not thirst. Too much water can carry away nutrients, foster fungal spores and disease and stress the lawn.