Buick/Olds: 1995 Buick Lesabre, buick lesabre, moist conditions

Question
I have a 1995 Lesabre with low mileage. When the vehicle gets wet like in a car wash or under very moist conditions, the parking lights go on automatically and drain the battery.  They can not be turned off without disconnecting the battery.  This is a vehicle which is in original condition which my father purchased new.  Any Ideas?  Short?  Thank you.  

Answer
Rick:

Well, I've done some homework and found out that there is a possibility of the main fuse relay under the hood to be getting too wet and allowing a current to pass through the headlight/fog/parking light relay. This is located on the right hand side of the the engine compartment. This is NOT a common problem, but I've found out that the solution is quite simple. Just give a quick look to the fuse relay under the hood, open it up and check for signs of corrosion.

If you see any, clean the corroded connections and then seal up the box (you can use duct tape if you want). This should help, if it continues, give me a quick line and I'll get back to the books to see if there's another line of defense.