Why is the backseat floorboard damp all the time

What is your question?

Cannot determine where water comes from. When it is parked outside and it rains, there will be water standing on the floor behind the front passenger seat. The car has a sunroof but has rarely been opened. Checking it for possible leakage has not revealed it is the cause.

What makes this problem better or worse?

When it rains or moisture in the air

How long has your 2014 Nissan Altima had this problem?

2 months