Hello XXXXXXXXXX, Naturally the first thing I would say is remove the lower dash panels and sit on the floor with a flash light and let someone just run the hose so the water runs down the windshield and see if you can see where the water is coming in. What I will tell you is under the plastic cowl that is under the windshield wipers there is an area where fresh air enters the interior. It is on the passenger side. Many times there is a rubber seal or deflector that gets dislodged and allows water to enter the interior. The second possibility along the same lines is on that same side there is a housing and the seal on the bottom of the housing may have deteriorated allowing water to flow under it. You have to remove the cowl to inspect if this is the case. Another possibility but I'm sure it's been checked is the evaporator a/c drain. This would cause condensation to back up into the car from the A/C housing. It would follow the use of air conditioning or defrosters. These are the places I think will lead to dry land for you. I'm here, so let me know if you need anything else as you proceed.
Your JA Expert,
Ivan
ASE Certified Master Technician
ASE Master Tech w/ 19 years in the field. Self employed for 9 years. Member of AUTOLAB radio show.