About to leave, truck batteries are dead question

This may sound like a silly question but did it rain over night when you came outside and found the truck batteries dead ?
The reason I ask is cause I have a early 1999 F350. Sometimes after a good rain what happens is water will get to the inside of the outer door handle where the electrical switch is for the inside illumination lites and cause them to come on and run the batteries down.
Ford may have corrected this on later models.