Why is the driver's side floorboard and under the seat soaked after rain

A clogged drain or seal is bad. Windshield or door seal, clogged cowl or sunroof drains. Sit in the car with someone spraying the car down with a hose to see where the leak is coming from.

I have removed the driver's seat and taken up the carpet. The carpet is wet from the floorboard in the front to the floorboard in the backseat area. The was water pooled in various small indentations found on the black plastic AC/heat duct that connected to what looks like a valve controlled vent just under the dash with the center console. At this juncture I am thinking it could be an occluded condensation drain hose. If the heater coil was leaking would there not be a smell like that of antifreeze? The most pronounced odor is one similar to mildew. I absolutely do not want to go to the Lexus dealer. They will charge me probably a couple of thousand dollars to unclog a drain hose. This is not an answer but further clarification of a long term leak that I have failed to notice. Please advise as far as my next step.