How long to water grass in the summer depends entirely on your specific sprinkler system and lawn conditions. The goal of summer watering is to deliver a precise volume of water to the soil, not to water for an arbitrary amount of time. Watering inefficiently often leads to shallow soaking, which leaves the grass vulnerable to heat stress. Achieving a healthy, resilient lawn requires calculating the exact time needed to meet a specific weekly water volume.
The Goal of Deep Watering: Required Volume
The foundation of summer lawn care is practicing deep, infrequent watering. Most common turf grasses require approximately 1 to 1.5 inches of water per week during peak summer heat to stay actively growing. This volume encourages grass roots to grow deep into the soil profile. Shallow, daily watering keeps moisture near the surface, training roots to stay short and making the lawn susceptible to drying out quickly.
When watering deeply, moisture penetrates the soil to a depth of six to eight inches, where the bulk of the root system should be located. Deeper roots can tap into a larger reserve of water, making the lawn more drought-resistant and resilient against high temperatures. Deep soaking also prevents the surface from staying constantly wet, which helps reduce the environment where common lawn diseases and fungal issues thrive.
Determining the Run Time (The Catch-Can Method)
Because every sprinkler system is different—including water pressure, nozzle type, and coverage uniformity—you must determine your specific watering duration through a calibration test. This process is known as the “catch-can” method. The goal is to measure your system’s precipitation rate, which is the rate at which water is applied to the lawn.
To perform this test, place several straight-sided containers, such as empty tuna cans, randomly across one of your sprinkler zones. Run the system for a fixed period, typically 15 minutes. After the time has elapsed, measure the depth of water collected in each can and calculate the average amount.
If your cans collected an average of 0.25 inches in 15 minutes, you can calculate the total run time needed to reach the target volume of 0.5 inches per watering session. In this scenario, you would need to run the system for 30 minutes to apply 0.5 inches of water. This process must be repeated for every separate watering zone, as the output rate can vary significantly.
Optimizing Timing and Frequency
Once the correct duration is calculated, the focus shifts to when and how often to apply the water. The optimal time for summer watering is in the early morning, ideally between 4 AM and 10 AM. Watering during this window minimizes water loss to evaporation because temperatures are lower and winds are calmer.
Watering in the morning ensures the grass blades dry quickly as the sun rises, which prevents the development of fungal diseases. Keeping the grass canopy wet overnight creates an ideal humid environment for pathogens to colonize. Frequency should be deep and infrequent, applying the calculated duration only two to three times per week, rather than daily shallow cycles. This schedule allows the soil surface to dry slightly between waterings, forcing the roots to chase moisture deeper into the soil.
Adjusting for Local Variables
Standard watering advice requires modification based on the specific characteristics of your lawn and local environment. Soil type dictates both the duration and frequency of watering. Sandy soil drains water quickly and holds less moisture, requiring shorter, more frequent watering sessions to prevent leaching past the root zone.
Clay soil is dense and retains water effectively but absorbs it slowly. Lawns with heavy clay soil need longer, less frequent watering periods to allow moisture to penetrate without causing runoff. On sloped areas or compacted clay, use the “cycle-soak” method. This involves splitting the total run time into two or three shorter bursts separated by a 30-minute rest period, which allows the water to soak in and prevents runoff.
Grass species also affect the total water required. Warm-season grasses, such as Bermuda or Zoysia, are more drought-tolerant and require less water than cool-season grasses, like Kentucky Bluegrass or Fescue, during peak summer heat. The schedule must also be adjusted for local weather, reducing the total run time or skipping a session if the lawn has received significant rainfall.