A lawn can be kept looking green and growing all summer and who doesn't want the best looking lawn on the block.
To help have a healthy green lawn all summer requires a couple of steps.
1) Cut the grass at 3 to 3 1/2 inches. This length gives the grass blades the ability to shade the soil helping to prevent high soil temperatures and to retain water better. The blades of grass will catch the water and funnel it down toward the soil. Longer grass blades will also encourage a deeper root system.
Cutting the grass short will cause the grass to develop shallow roots, dry out the soil faster. This can cause the lawn to develop bare spots which weeds will be happy to take over.
2) Water deeply twice a week. You should try to water early in the morning to help avoid evaporation stealing the water from the lawn before it can soak in. Grass needs about 1 inch of water per week. If you water twice a week at 1/2 inch per watering you can simulate a heavy rain and are much more likely to keep the grass from going dormant. You need to use a rain gauge to be sure you are adding enough water, the water pressure and efficiency of your sprinkler will have a dramatic effect on how long it takes to get enough water down.
3) Be consistent. While you can keep the grass from going dormant by watering it you have to be consistent. Allowing the grass to go dormant , then watering it to bring it back just to allow it to go dormant again will stress and weaken the lawn. Unless you plan to stick with the watering it would be better to let the lawn go dormant for the summer .... but that is not going to dominate the neighborhood with the best looking lawn :)