The amount of water your plants need and when it is needed changes with the weather, length of day, and root depth. By regularly adjusting the watering schedule of your automatic irrigation system (unless you have a smart timer), you can maintain healthy, beautiful plants and avoid wasting water.
In the Pacific Northwest, the watering season typically lasts from April through September. Check this page for advice on programming your sprinkler timer for the upcoming week. Interested in receiving weekly watering advice straight to your inbox? Sign up for the weekly water advice email! From March to October, we’ll send you a short email once per week that includes our watering advice and tips.
This week’s watering advice
Updated: Friday, September 5, 2025
Conditions: It looks like mild days are ahead, and maybe some rain.
Watering recommendation:
- Established, high water use plants: If the soil is dry beneath the surface, water ½ inch once this week.
- Established, deep-rooted plants with deep mulch over the soil: If the soil is dry beneath the surface, water slowly and deeply until the top 6 inches of soil is wet.
Principles for watering trees
Established trees have deep roots and need infrequent watering, typically once a year in July. To water them effectively, follow these best practices:
- Water slowly to allow moisture to percolate into the soil, especially if it’s clay soil.
- Water deeply to at least 6 inches below the surface – or deeper if the roots are further down.
- Cover bare soil with arborist woodchip mulch to reduce evaporation and retain moisture.
By following these best practices, you’ll help your trees remain healthy while saving water.
Are you ready to replace your old sprinkler timer with a new weather-based sprinkler timer? Weather-based timers can reduce your landscape water use by up to 25%. You may be eligible for up to a $100 rebate! Learn more about the program and eligibility requirements.
Learn more about choosing plants that are well-suited to our climate and how to water them.
Do you need professional assistance? Check out this short list of local certified landscape professionals!
Choosing the right run time for your system
Each watering should apply a ½ inch of water. The application rate of a sprinkler system depends on the water pressure, system design, and system efficiency. Below are some general ranges of typical run times based on the precipitation rate of your sprinkler heads:
| Head Type | Nozzle Description | Run Time* for a ½ inch | If Using Cycles** | |
|---|---|---|---|---|
 | Spray Head | Sprays like a fan | 15-23 minutes | 3 cycles of 5-8 minutes |
 | Rotor Head | Single spray that rotates | 30-75 minutes | 3 cycles of 10-25 minutes |
 | MSMT Head | Multiple single sprays that rotate | 50-75 minutes | 3 cycles of 17-25 minutes |
**Cycling Recommendation: To prevent runoff and ponding in areas with clay soils and/or slopes, divide the run times into three cycles to allow the ground to absorb the water. Additional cycles are created by utilizing more than one start time combined with shorter runtimes.
If you have drip irrigation, follow these guidelines that include how many minutes it takes to water ¼ of an inch:
