During hot summer weather, lawns generally require 2.5 centimetres (1″) of water every five to seven days. Without this amount of water from rainfall and/or irrigation during periods of high temperature and/or drought, Kentucky Bluegrass stops growing and turns brown.
Water only when the lawn needs it; just before it begins to wilt. When the colour becomes bluish-green and footprints remain for more than a few seconds after you walk across it, the lawn needs watering.
The optimal time to water is early in the morning when winds are calm and water loss caused by evaporation is minimal. Evening watering may encourage fungal diseases by leaving the lawn too wet for too long. Try to avoid midday watering which causes inefficient water use on hot, sunny days.