WunderMap Historical Weather

Weather Underground's WunderMap includes historical weather records back to 1st January 2001.

"A calendar control above the map allows the user to select a date and view the historical weather records for that day. The records include radar, storm reports and even weather related photographs and webcam images taken on that day."

Example:

http://www.wunderground.com/wundermap/?lat=51.50813&lon=-0.02501&zoom=11&type=terrain&units=metric&pin=London%2C+UK&plat=51.50813&plon=-0.12801&date=2002-01-01&time=15%3A00&rad=1&rad.num=1&rad.spd=25&rad.opa=70&rad.type=00Q&rad.type2=&rad.smo=1&sat=0&stormreports=0&svr=0&pix=0&cams=0&tor=0&riv=0&wxsn=1&ski=0&tfk=0&mm=0&ndfd=0&fire=0&hur=0&ib=0&mits=0&dir=0

Source and more information:

http://googlemapsmania.blogspot.com/2012/02/history-of-weather-on-google-maps.html