Does not start in wet weather

I have a 95 Mazda Protege which has an coil interated distributor. I cannot start the car when the weather is wet (the snow is melting). I tested with spark test pen and found no spark at all. I tried to test the resistence of coil from A and C terminal, found almost infinite resistence in primary coil test, and infinite resistence in secondary coil test. The input power is 12.5 volt with no problem. When the weather dried out next day. It started right away. I check the primary and secondary coil test again. Got the same infinite resistence again. What should I do next.