There are several possible leak sources with the most common being the air vent for the blower. Other possibilities could be moonroof, door vapor barriers, dash seams, floor seams, cowl seams, car alarms, and others.
I've repaired automotive water and wind leaks for almost 16 years. Email me at
leak.solutions@yahoo.com and perhaps I can either help you or give you the number of someone who can.
Thanks,
Terry