Driving when wet? Leaving it out when wet? After washing (especially engine compartment)?

Having a problem starting when the weather is wet.  New wires, new spark plugs, new coil.  I have a Chinese knock-off electronic distributor which I also had on another y-block with no problems (same model but different distributor).  I'm not saying it's the distributor, but that's my suspicion.  Where do I start?