About CIMIS Weather Stations

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, the model substitutes 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.

Access is 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, organized for pest management, is accessible from the UC Statewide IPM Project. Station-specific information, such as the latitude, longitude, and elevation is available on the CIMIS website.

Backup Stations & Error Messages

Data from a backup/substitute station, determined by the UC Statewide IPM Project, is used when data is unavailable from the weather station you selected. Stations are chosen which have similar climate conditions, however not all stations have substitutes. The following codes appear on your report when data from another weather station is used or when data is unavailable.

H = Up to 6 hours estimated by interpolation
There were 6 or fewer hours missing.  Data was interpolated from an estimation of the surrounding weather data.

S = Data from substitute station used
More than 6 hours missing.  Assumption of full day lost.  Data was taken from the primary or secondary substitute station.

P = No substitutes with data available
Data from previous day used.

N = Data not available
Daily CIMIS data has not been collected, usually because of network problem.  Past missing data will be collected when communication able to be connected.

No Data = Dates are out of the range that data was collected
This code will primarily be displayed in the research data in years before the 2004-2005 season. The research data collection season was expanded at the beginning of the 2004-2005 season to collect data from October through April. The traditional season is November through February. Prior to the 2004-2005 we didn’t try to collect data during October or April, hence "No Data."