Windshield seal?
Lower door seal?
Hole in floor ?
It could be a door seal or more likely the windshield is leaking.
windsheild leaks
it could be the window
There is obviously a leak in either the firewall/cowl area or the window seal.
One reason your floorboard is wet after it rains is that there may be rust holes in the floor or the floor pans are rusted out. A leak in the windshield seal may also be the cause of wet floorboards. Bad door seals or window seals can allow water to soak the floorboards when it rains.
Seals of the windscreen can be broken. If this is the case, whole windscreen needs to be replaced. Check by pouring water along the seals of the windscreen, you should be able to check if the water is trickling through into the floor of the car.
On my 82 280D I found the Sun roof leaked. ater resealing in. no more water.
"I have a 2003 Ford Explorer, the original owner. When it rains, the passenger side carpeting gets soaked. What causes this? I do have a moon roof."
It's located passenger side below windshield wiper. remove the cover at the base of windshield and pull it out. be careful putting back the piece of rubber if you don't want the passenger floor to become a lake when it rains
I had the same issue with a 2001 Alero and the Oldsmobile repair shop installed some sort of deflector inside of the door. Not sure what or where exactly but that is what they told me.
There are details you didn't give us.If your washroom floor drain only clogs when it rains, that may be a feature, not a bug. There are backflow traps that can be installed in floor drains to keep them from backing up and getting sewer water all over the floor. If your washroom floor is in the basement, the fact that it's clogging when it rains may be saving you from a big, nasty cleanup job.
The A/C drain plug is clogged. When it rains the humidity is high and the A/C will remove the moisture in the air. If the drain is plugged water flows to the passenger side through the blower motor and onto the floor have the drain plug cleared or you will be replacing your blower motor on a regular basis. Until then do not use A/C or front defrost setting.