NOAA/NCEI U.S. Climate Division Data Plotting Page: Division boundaries and county relationships.

NCEI provides a link to their climate division shapefiles (zipped). Please email them with questions.

NCAR has a netCDF file with the climate division boundaries available entitled "". NCL has the boundaries builtin to its plotting code as does GrADS.

You can find the counties that are in each division using this table provided by NCEI.