If your vehicle is showing water leaking from under the dashboard onto floor mats, here are the most likely causes and the parts you'll need to fix each one.
Condensation from the air conditioner normally drains outside the vehicle. If the rubber drain tube gets clogged with debris or insects, the water backs up into the HVAC case and spills onto the floor mats.
Leaves and debris can block the water drains in the cowl area at the base of the windshield. Rainwater pools up and overflows into the cabin's fresh air intake, dripping down through the blower motor.
Sunroof assemblies have drain tubes routed down the roof pillars. If these clog with dirt, rainwater overflows the track and runs down the inside of the A-pillar, eventually pooling under the dashboard.
The heater core circulates hot engine coolant to warm the cabin. If it corrodes and leaks, coolant will drip onto the floor mats, usually accompanied by a sweet smell and a greasy film on the windshield.
If the windshield was recently replaced and the urethane sealant wasn't applied correctly, or if the frame has rusted, rainwater can bypass the seal and drip down the firewall behind the dashboard.