Weird smell after rain

I have a 2001 S4.
There is a strange, "Musty", "Church-like" smell in my car whenver it's been sitting through a rain storm. Once I turn the car on, the smell
goes away. What does this mean?
Thanks,
Joe
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On 23 Oct 2006 10:25:40 -0700, " snipped-for-privacy@gmail.com"

Possibly you have cooties growing in your HVAC system.
Get a replacement for the cabin air filter, and a can of spray air cleaner/deodorizer. Make sure the HVAC system is set to fresh air intake (ie: not recirc mode) with all vents selected (top, middle, floor), open all the windows, remove the old cabin air filter, turn the fan on full, then blast some of the air cleaner down the cabin air intake. Then install the new filter...
/daytripper '00 s4 6spd
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See if small bits of leaves are stuck in drains, especially the ones in the doors and under the windshield. The door drains are easy enough to find with a mirror. Pour water down the windshield and see where it dribbles out.
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Thanks for your help Kevin and Daytripper.
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