Put your yard on a water budget! This link has information on how much water average plants need based on evaporation (water lost from the soil), transpiration (water lost from the plant), and precipitation received. Enter the dates for the period you would like to calculate. A positive water balance means there are that many inches of moisture available, no need to water. A negative balance means your plants require the equivalent of that many inches in moisture. Check this weekly during irrigation season to avoid over watering.