Developing a watering schedule depends on your lawn and what stage it's at. For an existing lawn that you're just looking to maintain throughout the summer, you'll want to water it about three times per week. The general rule of thumb is one inch of water per week.
If you have an irrigation system, be sure that each zone gets about 15 minutes of watering, three times a week. Every sprinkler is different, so we recommend getting a small measuring cup and testing your sprinkler to see how long it takes for the cup to fill up. If you're doing it manually, move around the yard every 15 minutes to make sure that every section has been watered.
It's also best to water your lawn in the mornings, especially if it's hot outside. The afternoon or evening heat can actually amplify the heat of the water and ultimately end up hurting or burning the grass. In the humidity of Northern VA, watering in the evening can also hold moisture on the grass, which is a recipe for fungus growth.