1. Keep your lawn long. Longer lawns do a better job of retaining water and standing up to heat. If you can, wait for a cooler day to mow and you will minimize water loss.
2. Be careful not to over fertilize your lawn. Extreme heat and too much lawn fertilizer are a bad combination. You’re likely to damage your lawn if you over apply.
3. Water in the early morning. Early morning watering is a good idea for lawncare throughout the year, but during a heat wave, it is particularly useful in fighting evaporation, which dries out your garden.
4. Water deeply. Light and frequent watering might seem like a good idea for a parched lawn. But in fact, a deep watering two or three times a week works best, particularly during heat waves. Deeper watering helps the lawn extend its roots deeper into the soil, where moisture can be found even after the top inch or two of soil dries out.
5. Mow late or early. This last tip is for you! Don’t mow your lawn in the blazing sun of a 90-degree day. Skip the heat stroke and wait till evening.
http://www.allaboutlawns.com/lawn-maintenance-care/seasonal-lawn-care/5-tips-for-grass-green. By Dawn West, All About Lawns Columnist