I gave up riding there in the wet. I'm not the quickest rider around there , but prefer dry , however if on four wheels i just do the laps at a reduced pace to learn the lines and quicks that you overlook at a pushing pace.
However it's fairly dry at the start gate at the mo;
http://nuerburgring.de/fileadmin/webcam/webcam.jpg Image can be refreshed every minute. Nice to see people getting laps in.