Does Watering During the Day Hurt Grass?

Efficiency

• Temperatures are typically lower, and winds lighter in the early morning -- from around 4 a.m. until about 8 a.m. As a result, less water evaporates, so more of it reaches grass roots. This makes early morning the most efficient time of day to water a lawn. You use less water to meet that 1 inch per week goal, and it also translates to a lower water bill.

Mold

• The worst time of day to water a lawn is in the evening. Grass stops photosynthesizing as the sun sets, so it is less likely to soak up water. Water may puddle, or the soil may stay too moist. Because the sun has gone down, less water evaporates, so grass blades stay wet. The combination of these two factors -- wet soil and wet grass blades -- produces the conditions molds and grass fungi need to flourish.

Midday Watering

• While watering during the heat of a summer day will not harm your lawn, it doesn’t help your bank account. A portion of the water evaporates before it reaches grass roots, so you end up using more water than you should, which costs you money. A little water sprinkled on grass during midday may help cool the the grass, reducing heat stress, but watering to achieve that 1 inch per week is best left for earlier in the day.

Checking for Moisture

• Plunge a screwdriver into the soil in the lawn. If it goes in easily, the soil probably has enough moisture and you don't need to water. If the grass blades have wilted, or turned a bluish-gray color, the lawn may be drying out. These are signs it needs water. You can also walk across your lawn and see whether your footprints remain in the grass blades. Well-hydrated blades spring back up quickly, while drier blades tend to hold footprints. Avoid watering just after a soaking rain, or even a few days before predicted rain. Watering at these times results in unnecessary runoff into sewers and streams.