To access current ET Data by phone, updated and recorded every Monday, call:

ET Hotline (English)   (949) 453-5451
ET Hotline (Spanish)  (949) 453-5452

To access year-to-date Daily ET - CLICK HERE

How the weather effects your water allocation
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 allocations to ensure that your landscaping receives sufficient water.

Within the IRWD service area, there are three distinct microclimates, known as the Coastal, Central and Foothill zones. The District 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.

Everyday, Coastal, Central and Foothill weather station data is transmitted electronically to IRWD where it is used in a formula to calculate evapo-transpiration (ET), or the amount of water needed by turfgrass to remain healthy in each specific climate zone. When the weather gets hotter or windier, your allocation goes up automatically. When it's cooler or rainier, your allocation decreases.

Keeping within your allocation makes good sense
The goal is to allow you the correct water allocation you need for your landscapes 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.

Employing state-of-the-art technology to help you water wisely
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 (CIMIS) stations around the state.

To find out more about the statewide system, visit CIMIS information

Current Evapo-transpiration Data

The following historical ET Data is also available:
2007 ET Data
2006 ET Data
2005 ET Data
2004 ET Data
2003 ET Data
2002 ET Data
2001 ET Data
2000 ET Data
1999 ET Data
1998 ET Data
1997 ET Data