The CDEC website provides access to a wide range in hydrologic data (stream flow, snow survey, etc.) collected in California. The following code and functions (attached at the bottom of the page) illustrate how to query CDEC, and graphically compare the May 2011 snow survey data with the historic record at 15 sites. Data in this format lend well to the "split-apply-combine" strategy. Integration of several figures (scatter plot, custom box-whisker plot) and graphical legend for bwplot is accomplished via the latticeExtra package. See in-line comments below for a more complete description of the code.
Note that snow water equivalent (SWE) from May 2011 (blue dots) is compared with the historic record (box-whisker plots) for the months of Jan-May. Pretty impressive snowfall!