your heater core is bad you may also experience steam in the windshield
you could have a heater core leaking or your windshield is leaking and the water is running down behind the dash and onto the floor.
There is a drain on the outside firewall that is clogged.
Are you running the air conditioner? If the drain line is plugged, it will leak water (condensation) onto the passenger side floor.
heater core may be leaking or hole in floor
Condensation from air conditioning?
heater core leaking
Antifreeze leaking from the heater core.
Water is leaking on passenger side floor board when heat is on
It could be the heater core leaking.
Heater core
when your heater core is shot it will leak on the passenger side of vehicle and your windshield will fog up most of the time
Your heater core is leaking. This is the part of your car that creates heat for the passenger compartment of your car. There is no fix for a leaking heater core except to replace it.