in the october 2007 issue of rc car magazine they have a article all about preping your car for wet weather, I will list everything they cover. Also just to make sure you know, even with all this preperation if a drop of water somehow gets to the wrong spot that electronic can get ruined these are just steps to prevent it as much as possible. this is also for performance but for wet weather racing you want more than just electronic protection, you want to keep your whole car protected
Balloon your reciever
Put silicone around where your wires exit the servo, and thick grease on the base of the output gear on the servo
Duct tape on the suspension arms, put some on the bottom and a sheild in the front to keep mud from building up on the arms
Wheel scrapers
Lube your bearings before and after
piece of lexan in front of your air filter to keep the water out of it
So basicialy ballon your reciever, put something like shoe goo around where the wires come out of the reciever and thick grease around the base of the output shaft on the servo