This is what happens when manufacturers remove the good old gutter rails from the roof of nearly all modern cars - if it's raining water will get into the car as the curve of the doors goes into the roof line.

I have had this now on all cars I've owned since 1991.

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Me:
Current: 2011 E71 40D Vermilion Red/Beige Nappa

Wifey:
Current: 2012 R80 Countryman SDX Green/Cream