My 2001 Chevy Express Cargo Van V6 base model. Runs great most of the time but when it rains, it turns over but won't start. I've changed the fuel pump, plugs, wires, cap, coil, and icm. If she's been running and it rains there are no issues with starting her up, but if she sets overnight and it rains, the issue happens. I think it's more of a condensation issue. I have a Ryobi mini leaf blower that I've used to try and blow and dry anything like the coil but I still see no change. HELP!

 

Examine the computer case, under the master cylinder.

The first 2002 I got ran great when dry but after a wet, windy day would not start, then ran badly when it did start. It turned out the computer was full of water where the case had corroded. How it got in there while it was just sitting, I don't know, but it's worth a look and if there's not too much damage, RTV the heck out of it.

another thing to look at is the distributor body itself can crack, which would let moisture inside and possibly prevent a start. Have you checked under the cap when it won't start?