Most lawn authorities suggest that the lawn only needs the equivalent of one inch of water per week to keep it green all summer. This amount of water can be from sprinkling or a combination of rainfall and watering. One of the ways in which to measure the amount of water you are applying to the lawn is to set out three or four coffee cans, then measure the amount of water that collects in them after sprinkling for an hour or so. It is estimated that sprinkler water evaporates four to eight times faster if the sprinkling is done during the warmer afternoon hours. So early morning is by far the best time to do any watering.
Some specialists suggest that grass clippings be left on the lawn during the hot summer months.
The clippings serve as a moist retentive mulch. However, I haven't been able to convince my wife that this is a good idea. She says, they all end up on the carpeting in the house. So we collect and compost our grass clippings. And, of course compost or other organic mulches are ideal to use in the garden because of their ability to absorb moisture and retain it longer in the soil.