Raining inside my car dream

So I was riding in a car that appeared to be driving itself.  My sister was in there and I said something to her that I had on my mind for a while.  She suddenly dissappeared and this down pour of water like rain came down on top of me. I got frightened that it would cause th car to become dangerous. I felt around behind me to find a button to turn the rain off but instead I pressed something that made it ppur even harder and it started to become warm and lovely to be under!