Water leak from inside the car

[jcdarrin]

I have a water leak coming from under the passenger front seat into the right-side rear footwell, soaking the carpet and even producing standing water. We are in a drought so it is not from outside and it appears to happen when we are not driving. It has happened three random times and then stops for a random period. I find no common situation to explain it. There are two black plastic vents under the seat and I don't know if they are involved.

[RX400h]

Could a drain be backed up from previous rain?