My little girl did this on my old golf when she was playing with the keys. Unbeknown to me all 4 windows fully down overnight and it pished it down all night.
Woke up to find 1 inch of water in all the foot wells and everything soaked. Door cards, seats, speakers, switches - the lot.
Took me a week to dry it out with the car sitting on my drive with the engine running and the heater on full. Had to go out every half hour and rev it to get the temp back up as it kept dropping. Probably took a month for the windows to stop steaming up.
Not a nice experience having to drive round sat on a bin liner. You get a right sweaty bum crack.