Why is the rear drivers floor board wet no windows have been opened
As it is still under warranty take it back to the dealer, don't attempt to clean it out as you might wipe out any water trails that can help locating the leak.
I had a vehicle that did that and it turned our to be the back windscreen. the water can run down the wheel arch and get in any where. if it is, you'll never find it. trust me, if there's a way for water to get in, it will find it.
did you check to see if the heater cole is likeing
Others have had this problem, there is a factory defect that their wasn't a recall,for. It should be fixed by the dealer for free. It has something to do with the windshield leaking when it rains.
Looking for a Used Altima in your area?
CarGurus has 81,564 nationwide Altima listings starting at $1,200.
Search Nissan Altima Questions
Nissan Altima Experts