One frequent cause of a wet floor, is blocked drain holes in the scuttle below the windscreen.
These drain holes are frequently located right up against the wings and get full of leaf debris. When they get blocked the rain water cannot drain away and it builds up, finally entering the heater air intake, which for some reason car designers locate in the same scuttle!
Remove the debris and pour water into the scuttle to check that it is draining out. Sometimes the drain tube gets blocked, it is possible to clear it with curtain wire, or blast it with a water jet from a hosepipe.
AcmeUK, March 2010