The current weather data is provided in TMY3 format derived from the NREL SAM data sets available at http://rredc.nrel.gov/solar/old_data/nsrdb/1991-2005/tmy3/zip/alltmy3a.zip
The files have been renamed from the NREL FN numbered scheme to the GridLAB-D [State]-[Location].tmy3 file naming scheme.
For details on TMY3 data format, see www.nrel.gov/docs/fy08osti/43156.pdf.
As of Version 4.2, GridLAB-D can directly manage local copies of this weather data using the gridlabd weather command.