I missed the part about after driving in a major rain storm, but were you parked during any part of the rainstorm?
You're going to have to do some forensic analysis on the origin.
I didn't see any mention of how you're drying things out. I've used a wet dry vacuum followed by dehumidifiers for at least a week. In the meantime I'd be inside the area that's wet during a rainstorm looking for active dripping. With a dry carpet to start with it will easier to locate the origin of the leak by touch and sight.
2006 Sunseeker 2860DS Ford V10 5 sp. Torq-Flite w Tow/Haul
Winegard T4 In Motion Satellite Dish
Furion Rear Camera, RecPro 70" Recliners
Mohawk Luxury Vinyl Plank Flooring
2013 AWD Acadia Denali, Blue Ox Equipped