Saving Water Partnership

Calculate how much to irrigate your landscape

Use the Water Budget Calculator to determine how much water a lawn needs, based on the size of your irrigated landscape and yearly weather averages for the Seattle area.
Use the Sprinkler Scheduler to create watering schedules for automatic in-ground irrigation systems, based on the types of your plantings and watering system.

ET (Evapotranspiration Rate) is how much water your plants use—thus, how much water you need to replace to keep your landscape green. Watering more than this is a waste of money and water.

Raw Data

Users who need access to weekly raw ET/rainfall data in CSV format can download the data by clicking here.

Average ET, Actual and Effective Rainfall and Irrigation Index (for the irrigation season)
Month ET Actual Rainfall Eff. Rainfall (33%) Irrigation Index
April 2.38 2.87 0.89 53%
May 3.14 2.60 0.86 70%
June 3.50 2.00 0.66 78%
July 4.46 0.52 0.17 100%
August 3.71 1.11 0.37 83%
September 2.54 1.29 0.43 57%
Totals 19.73 10.24 3.38  

Please note:
irrigation is not needed in the Seattle area during the months of October through March.

 

Past Year's Data Comparisons


* Note
As with most technology, weather stations and the technology that ties it all together, are sometimes victims of malfunctions. Occasionally the weather data produced and posted on this site might be temporarily inaccurate. Please check the data being used for obvious errors. (for example: if the ET one day is .13" and the next it is 300" then caution is advised)

Summary of weather information for the Seattle area.

Click on a station for local weather data for irrigation management.
By clicking the links below, you acknowledge that you have read and agree to these terms of use.

Map of the Seattle area


Terms of Use

This data is provided at no cost to the user. The user accepts all responsibility and agrees to hold harmless the IWMS, Seattle Public Utilities, the Saving Water Partnership and the owner/operators of the weather stations of the PNWLWN (Providers) in case of errors with this data obtained from this website. The Providers shall not be responsible for any damages, direct or indirect caused by the use of this site or the weather data displayed herein. The user agrees that there is a potential risk involved with the use of this data and that errors can occur with the technology (or human error) used to supply and calculate this data.
 
The user witnesses that they have read and agree to these terms.

Bothell

(Weather station inactive - data not up to date)

18305 101st Avenue N.E.

 

Last Weather Update:12/8/2013 9:00:00 PM

 Last Web Update:5/1/2014 - 12:17:04 PM
Air Temperature  
Last Hour Average 7.8°
Daily Average 6.4°
Daily Maximum Temperature 19.6°
Daily Minimum Temperature F
 
Solar  
Solar Radiation Average 0.0w/m2
 
Relative Humidity  
Relative Humidity Average 76.6%
   
Wind  
Wind Speed Average 0.0 MPH
 
Rain Total Effective
Rain (Last Hour) 0.00" 0.00"
Rain (Last 24 Hour) 0.00" 0.00"
Rain (Last 7 Days) 0.27" 0.27"
 
ETo  
Todays ET 0.01"
Last 24 Hour ETo (Evapotranspiration) 0.01"
Last 7 Day ETo (Evapotranspiration) 0.08"
 
Irrigation Requirements  
Last 24 Hour 0.01"
Last 7 Day -0.19"
Irrigation Cycles Per Week 0

 

Last Year Summary By Month  This Year Summary By Month

 

Graphs
Last 7 Days
Humidity & Temperature ET & Rain Solar & Temperature Wind
Year To Date 
Humidity & Temperature ET & Rain Solar & Temperature Wind

 

Historical and Past Years Data
Current Month
January March May July September November
February April June August October December
Last Year

Woodinville

(Weather station inactive - data not up to date)

17238 NE Woodinville-Duvall Rd

 

Last Weather Update:12/8/2013 8:00:00 PM

 Last Web Update:5/1/2014 - 12:17:06 PM
Air Temperature  
Last Hour Average 19.3°
Daily Average 19.3°
Daily Maximum Temperature 33.3°
Daily Minimum Temperature 9.3°
 
Solar  
Solar Radiation Average 0.0w/m2
 
Relative Humidity  
Relative Humidity Average 83.9%
   
Wind  
Wind Speed Average 0.0 MPH
 
Rain Total Effective
Rain (Last Hour) 0.00" 0.00"
Rain (Last 24 Hour) 0.00" 0.00"
Rain (Last 7 Days) 0.62" 0.62"
 
ETo  
Todays ET 0.01"
Last 24 Hour ETo (Evapotranspiration) 0.01"
Last 7 Day ETo (Evapotranspiration) 0.08"
 
Irrigation Requirements  
Last 24 Hour 0.01"
Last 7 Day -0.54"
Irrigation Cycles Per Week 0

 

Last Year Summary By Month  This Year Summary By Month

 

Graphs
Last 7 Days
Humidity & Temperature ET & Rain Solar & Temperature Wind
Year To Date 
Humidity & Temperature ET & Rain Solar & Temperature Wind

 

Historical and Past Years Data
Current Month
January March May July September November
February April June August October December
Last Year

JeffersonPark

(Weather station inactive - data not up to date)

1600 South Dakota Street

 

Last Weather Update:12/8/2013 9:00:00 PM

 Last Web Update:5/1/2014 - 12:17:05 PM
Air Temperature  
Last Hour Average 27.2°
Daily Average 24.5°
Daily Maximum Temperature 31.1°
Daily Minimum Temperature 18.6°
 
Solar  
Solar Radiation Average 0.0w/m2
 
Relative Humidity  
Relative Humidity Average 58.3%
   
Wind  
Wind Speed Average 0.0 MPH
 
Rain Total Effective
Rain (Last Hour) 0.00" 0.00"
Rain (Last 24 Hour) 0.00" 0.00"
Rain (Last 7 Days) 0.07" 0.07"
 
ETo  
Todays ET 0.01"
Last 24 Hour ETo (Evapotranspiration) 0.01"
Last 7 Day ETo (Evapotranspiration) 0.10"
 
Irrigation Requirements  
Last 24 Hour 0.01"
Last 7 Day 0.03"
Irrigation Cycles Per Week 0

 

Last Year Summary By Month  This Year Summary By Month

 

Graphs
Last 7 Days
Humidity & Temperature ET & Rain Solar & Temperature Wind
Year To Date 
Humidity & Temperature ET & Rain Solar & Temperature Wind

 

Historical and Past Years Data
Current Month
January March May July September November
February April June August October December
Last Year