Selecting the correct time to water the lawn is important so that you can use your water supply wisely. Watering at the correct time of the day and at the proper frequency reduces the risk of lawn diseases due to stagnant water sitting on the grass. Using an automated timer helps to make sure your lawn is receiving water at the right time.
Early morning is the best choice for watering your lawn. Temperatures are cooler in the early morning, allowing the water to penetrate into the lawn without evaporating quickly, like when temperatures are at their highest midday. Winds are less frequent in the early morning, so that any water you place onto the grass is less likely to evaporate because of the wind. The air in the early morning is also very humid, resulting in dew that adds to the moisture on the grass, so that the grass receives extra water at that time of day. If you accidentally over-water the lawn in the early morning, the water has all day to evaporate so that there is no stagnant water sitting on the lawn at night, which can lead to lawn disease.
Late afternoon can be a good time to water your lawn, as long as you do not over-water. Placing too much moisture on the lawn in late afternoon does not give the lawn enough time to dry before night fall, resulting in water sitting on the lawn, which can result in lawn disease. Late afternoon has lower temperatures than midday, so the excessive heat is not evaporating the water before it has a chance to penetrate the soil.
Watering the lawn twice per week is more desirable than watering once per day. If plants receive a good soak once or twice a week they begin to develop deep roots, whereas with a light watering the water stays close the the surface of the soil, resulting in a shallow root structure throughout the lawn.