If you're looking for long term climate summaries, this site ought to give you plenty to work through: http://www.wrcc.dri.edu/summary/climsmwa.html
Glacier, Newhalem and Baker Dam stations are closest to the areas you mentioned, though obviously not really indicative of 'mountain' conditions.
You might be able to do a little digging to get archived data from the RAWS or SNOTEL stations. Lots of historical data are out there on CDs, old newspapers, etc., depending on how hard you want to dig.