The California Irrigation Management Information System recently launched a new facility to deliver XML-based real time weather data to irrigators and water agencies as a means of supporting automated water conservation strategies. Water management experts can obtain hourly, daily, monthly, and historical data over an extended period of time. CIMIS was established in 1982 by the California Department of Water Resources and the University of California at Davis, and uses a network of some 120 automated weather stations. The sensors at these stations measure reference evapotranspiration and meteorological data such as solar radiation, vapor pressure, dew point, relative humidity, net radiation, air temperature, wind speed and direction, average soil temperature, and precipitation. This data is delivered to growers, landscape managers, golf courses to assist in water budgeting and conservation. As a further means of supporting automated water usage, CIMIS program is in the process of incorporating satellite data to map reference evapotranspiration for the entire state.

A typical weather report consists of 14 pre-determined parameters: ETo [reference evapotranspiration]; precipitation; solar radiation; average vapor pressure; maximum, minimum, and average air temperature; maximum, minimum, and average Relative Humidity; dew point; wind speed; wind run; and average soil temperature. Users can configure weather feeds to pull data from a number of weather sensors.

"The 24 hourly ETo values for the day (midnight to midnight) are summed to result in daily ETo. The inputs used in this equation from the CIMIS weather stations are these hourly values: (1) Net Radiation; (2) Air Temperature; (3) Wind Speed; (4) Vapor Pressure. Air temperature, wind speed, and relative humidity are measured directly at each weather station. Vapor pressure is calculated from relative humidity and air temperature. Hourly net radiation is estimated using a method developed by the University of California. This method uses solar radiation, vapor pressure, air temperature, and a calculated monthly cloud coefficient (CK)."

A number of syndicated weather data feeds are being implemented for combining GIS and weather information. See for example CustomWeather.