Hourly air temperatures, collected from the California Irrigation Management Information System (CIMIS) weather stations, are used to calculate chilling units. Each night, Pomology Weather Services downloads the data through the CIMIS system. If data is temporarily unavailable from a station, we substitute data from a predetermined "backup station" (a nearby CIMIS station that can be used to fill in data gaps).

CIMIS, developed by the California Department of Water Resource and the University of California at Davis, is a repository of climatological data collected at more than 100 computerized weather stations located in many areas of California. Operational since 1982, it has recently been redesigned to use the latest database technology.

Access is now possible through the Internet and operates 24 hours a day, every day of the year except during maintenance hours. Providing information for improving water and energy management through efficient irrigation practices is the primary use of the CIMIS system. Weather data is collected from each weather station site and automatically transmitted to a central computer located in Sacramento. The weather data is analyzed for accuracy, then stored to provide on-demand, localized information.

The CIMIS Web site provides weather station information and access to raw data, weekly and monthly data, and normal year ETo tables by county.

Access to specific weather data, orgainzed for pest management, is accessible from the UC Statewide IPM Project. This site also provides weather station news and the latitude, longitute, and elevation of specific CIMIS stations.