Watering requirements for your lawn will depend on a lot of different factors and will vary considerably from lawn to lawn and area to area. In general, in the hot summer months, lawn made from bluegrass or ryegrass will need about 2¼ inches of water every week. less in cooler weather. If your lawn is made from fescues less frequent watering is needed as this type of grass has a deeper root system and can store more moisture between waterings.