Driver side floor leak after rain or car wash on 2008 Lincoln MKX

How do I troubleshoot a leak to the floorboard, driver side after a rain or car wash? This car is garaged so I know it's only after a rain or long car wash. Tips appreciated. Regards.

Asked by for the 2008 Lincoln MKX
clean the drain. its under the grills back of your hood... you have one on both sides...
Do I need to remove the plastic cover over the windshield wipers? Or, just use a car wash wand and spray directly into the grill. I tried to find the location to clean but was unsuccessful. Thanks.