Truck Won't Start when it is Damp out

I am not sure what they are thinking, but the first thing I would look for is a cracked or loose distributor cap, just replace it, they are fairly cheap and do the rotor also, and also look for cracked or loose spark plug wires, if they are old they should be replaced also, I found out the hard way that they only last for so long, then they dont give a good spark, you can also try to dry out the cap with ether or starting fluid, just make sure that if you try this, THE CAP IS DRY, before trying to crank the engine, DUHHHHH, what does starting fluid do with a spark, BOOOM.