How Long to Water Lawn

Source:  Texas A&M AgriLife Research & Extension Center at Dallas

Learn how to determine how much to water your lawn using ET Weather Data.

Early morning is considered the best time to water. The wind is usually calm and the temperature is low so less water is lost to evaporation. The worst time to water is late evening because the lawn stays wet all night, making it more susceptible to disease.

Determine how much water your sprinkler system applies to each watering zone

1.  Place small containers or cans on your lawn in each watering zone.  Tuna cans work great for this but you can use other similar-sized containers.

2.  Run your sprinkler system for 15 minutes in each watering zone.

3.  Measure the depth of the water in each container using a ruler.  Write down the measurements.


  • Zone 1 = 1.5 inches
  • Zone 2 = 2 inches
  • Zone 3 = 1.25 inches

4.  Multiply each measurement by 4 to get the hourly precipitation rate


  • Zone 1 = 1.5 inches x 4 = 6 inches per hour
  • Zone 2 = 2 inches x 4 = 8 inches per hour
  • Zone 3 = 1.25 inches x 4 = 5 inches per hour


Use Weather ET Data to Determine Sprinkler Zone Run Times

1.  Go to:

2.  On the homepage, select a station nearest to you from the Current Stations drop down list or by clicking on a map location.

Select ET Station Closest to You

Select ET Station Closest to You (click for larger image)

3.  On the next screen, select Home Watering

Select Home Watering

Select Home Watering (click for larger image)

4.  Use the calculator on the next screen to calculate the sprinkler run time and frequency for each watering zone.

  • In Step 1, input the sunlight exposure for each watering zone (full sun, part shade, full shade).  Then select your turf grass species. The value for Water Requirement for Turf Type will then be automatically added to the form.
  • Step 2, Precipitation Parameters, should automatically be inputted for you. If not, then click the Show Weather Data link above the form and input the total Rain value.
  • In Step 3, input the hourly precipitation rates you calculated for each of your watering zones.
  • Select the calculate button.
  • Total Run Time, Irrigations/Week, Run Time/Irrigation will be shown.  Record these values for each watering zone and place a date next to this set.
  • Periodically check the website and recalculate.

Calculator (click for larger image)

View more Water Conservation Resources for Homeowners »



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