Weekly Watering Number | Regional Water Providers Consortium
to receive your Weekly Watering Number.
Oct 28–Nov 3, 2021more info

Waterwise Tip:

It’s time to stop watering for the season and start thinking about winterizing your irrigation system for upcoming colder weather. Get your sprinkler systems, hoses, backflow devices, and outdoor faucets ready with these tips.

Watering Guidelines:

The rain is here to stay, and you will not need to water this week (or next week, or likely until watering season starts up again in April). 

Your next Weekly Watering Number will be posted in April 2022.

Weekly Watering Number

Everyone can have a blue thumb – start watering smart today with the Weekly Watering Number! 

Here in the Portland metro area, we like to joke that summer officially starts July 5th. But, while summer weather may finally kick in then, we often start watering our lawns and gardens the first or second warm-ish spring day. And, we keep on watering them until the fall rains begin.

What many people don’t know is that established plants (those that have been in the ground a year or two) usually don’t need to be watered until the warmer temperatures set in and dry out our clay soil. In fact, spring can be a great time to conserve water!

That’s where the Weekly Watering Number (WWN) comes in. Sign up for the WWN and we'll tell you when to start watering and how much to water each week through mid-October. We will also send you a Weekly Tip, along with your WWN, throughout the watering season to help you use water efficiently outdoors. If you have questions about your subscription to our newsletter or meeting notices, or you would like to unsubscribe, email us.

The form is also available at this link.


How to get started

Before you can start using the WWN, you will need to take 15 minutes to figure out how long it takes your watering system to water one inch. Don’t worry, this is a one-time thing! Once you have this information, you can use it adjust the amount of water you give your landscape or garden throughout the irrigation season.


How to use the Weekly Watering Number

Different plants have different water needs and you can use the WWN to tailor the amount of water you give to different plant types (e.g. lawns, perennials, vegetable, trees). See below for more information on how the WWN can be used for lawns and other types of plants.

The other key to watering efficiently is to adjust the amount you water as the weather changes throughout the irrigation season. For example, we’ll let you know if a rain storm or heat wave means you should change how much you water – and we will tell you how much of a change is needed.

Can I use the Weekly Watering Number for other types of plants?

Yes. The WWN is the amount of water in inches that your lawn will need each week. Different plants have different water needs, and you can adjust the Weekly Watering Number for different plant types with these general guidelines:

  • Lawns: 100% of WWN
  • Shrubs and Perennials: 50% of the WWN (newly planted plants may require more water)
  • Vegetables: 75% of the WWN (new starts may require more water)
  • Trees: WWN is not recommended for trees. Newly planted trees need regular watering for up to the first couple of years, while established trees may need a deep soak or two in summer.


Why does the Weekly Watering Number change each week?

The WWN changes with local weather conditions. So, in the cooler, wetter spring it tends to be lower, and in the hotter drier summer it tends to be higher.


What does my zip code have to do with this?

Sometimes weather is warmer, cooler, wetter or dryer where you live than it is across town. We customize your WWN based on your specific zip code so that it is more accurate.


Where does the data for the Weekly Watering Number come from?

The Consortium contracts with a weather forecasting service to provide the data, including rain fall, evapotranspiration, solar radiation, needed to generate the WWN.


Why do you use historical data to create the Weekly Water Number?

The WWN is based on the previous week's weather (heat, rainfall, wind, etc). It is meant to replace any moisture that your plant's soil lost the previous week.