F150 Ford, rain and humidity prevents starting. It's not the distributor or plug wires?

It's not the distributor or the wires. Fuel pump is pumping? If it's already running when it's raining, it will continue to run just fine. It's definitely condensation somewhere?

Year-1990

It could still be the distributor cap or plug wires. Once it's running engine heat will keep the humidity or rain from being a problem.

Pretty much it has to be cap, rotor, wires or coil. Lift the hood in the dark and look for stray sparks when it is running.

Ignition module poorly grounded dura spark ignition box even a corroded ignition module, behind it. But what year i'm guessing here okay 1990 I would go directly to the module and start there also look down in the distributor body is there corrosion and grasp the distributor rotor post does it have excessive side to side movement if so replace it when its hot the metal expands taking up some slack but not all of it what about the tiny almost useless fuse-able link for the entire charging system if you have ditched it yet for a self resetting breaker you should think about that too but i think your issue lies in your distributor and or module or both a;so check for stray and scattering spark at the plugs and the cap &rotor also check for cracked dist cap