California Climate Tracker

Monthly station data, taken from cooperative observers (COOP*), along with gridded data from the PRISM database, are used to assess climate across the state. The primary variables that are considered in this process are monthly average mean temperatures and monthly precipitation totals.  

*Cooperative Observer Network (COOP), managed by the National Weather Service, consist of up to 12,000 weather stations across the United States that report daily measurements of precipitation and/or temperature.  

We consider COOP stations across the state that reported over 75% of observations over the time period 1949-2005, and continued to report in 2006.  A total of 195 stations across the state are included in this analysis.  We consider COOP station data along with the PRISM database dating back to January of 1895. Temperature data from the COOP stations have been adjusted for inhomogeneities, a procedure used to "correct" for non-climate shifts in temperature. 

Statewide, regional, and station based graphics and time series are produced each month. Preliminary products for the last available month will be updated by the 3rd of each month, once the initial COOP station reports come in. A second update will appear near the 10th of each month once the PRISM dataset is updated. The COOP and PRISM products are combined into a single dataset to improve difficulties with sampling errors and the insufficiencies with each dataset. Data from up to twelve months ago is considered provisional, as data continues to filter in and undergoes quality control procedures. 




Publication Date: 2009

Authors or Affiliated Users:

  • J.T. Abatzoglou
  • K.T. Redmond
  • L.M. Edward

Related Organizations:

Resource Category:

Resource Types:

  • Climate science
  • Monitoring
  • Tool (general)

States Affected:


  • Air temperature
  • Precipitation changes

Go To Resource