Rough Idle when raining 1999

I have a 1999.5 2.0 with 70k seems to idle low and rough, but only when its raining. The alarm also goes off when it is raining but that I have found out is either a wire or the micro sensor in the door. The two problems seem to be around at the same time.. Any ideas? Anyway they could be parts of the same problem? Other than this , my little wagon is a dream.
cheers

I can't explain the alarm, but my 98 jetta ran very rough in the rain and it turned out to be a bad coil. If I am not mistaken, there is a recall on the A4 coils. You can verify that by calling your dealer or checking on www.nhtsa.gov. Follow the links to the recall and defect information. Hope this helps. Ray

Coil recall only applys to 1.8t models.

But yes, running rough when it rains out is almost always ignition coil or spark plug wire problems.