Rain or humidity Starting problem

I recently bought a 95 vw cabrio. I love how it drives and I got a great deal on it. It always starts right up but occassionaly it seems to have trouble starting if it's been raining for a while. I'm not talking about going through puddles either. The car is just parked in my driveway. Usually I open the hood and let the sun in and it starts up after a short time. Any ideas??

Ignition coils that fail when humid or wet are extremely common.