ET Weather Center

ET Hotline

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Coastal, Central and Foothill weather station data is electronically transmitted daily to IRWD where it is used in a formula to calculate evapo-transpiration, also known as ET, which is the amount of water needed by turfgrass to remain healthy in each specific climate zone. Outdoor watering accounts for 40 to 70 percent of water used in Orange County. With thousands of acres of valuable community parks, gardens and greenbelts within its boundaries, IRWD's billing system relies on accurate weather station data to provide landscape and commercial customers like you with site-specific budgets to ensure that your landscaping receives sufficient water.

Important Links

Potable Water Weekly ET Water Budget Data*

Recycled Water Weekly ET Water Budget Data*

Year-to-Date Daily ET

CIMIS Information

Weather Station Locations Map

*Weekly ET data should be up to date by Monday at 10:30 AM, 2019 data to be added to table at the end of the year

Historical ET Data

2018	2017	2016	2015	2014
2013	2012	2011	2010	2009
2008	2007	2006	2005	2004
2003	2002	2001	2000	1999
1998	1997

Weather Determines Your Water Budget

How Weather Affects your Water Budget: When the weather is hot or windy, your budget goes up automatically. When it's cool or rainy, your budget decreases.

Staying within Budget Makes Sense: The goal is to allow you the correct water budget you need for your landscape to stay healthy and attractive. Using more water than plants need is a waste of water, a waste of your money, leads to unhealthy plants, and can contribute to pollution-causing urban runoff.

Weather Station Technology Helps you Save Water

Advanced Weather Station Technology: IRWD uses the most advanced weather station technology, consisting of Campbell Scientific CR-10X Data Logger equipment, the same used by the California Department of Water Resources for the 100 California Irrigation Management Information System stations around the state.

IRWD has 3 Microclimates: Within our service area, there are three distinct microclimates, known as the Coastal, Central and Foothill zones. IRWD maintains a separate weather station in each climate zone to monitor exact wind and weather conditions, including air temperatures, relative humidity, precipitation, solar radiation, and wind direction and speed.