86 Prelude won't start after it rains

Probably a bad connection or corrosion at connections in wiring. I would start with the ignition system like a coil pack.

I doubt anything is getting wet, but you could be right on a bad connection. You could have enough humidity in the air after a rain to cause a weak connection to fail completely. It could also be a faulty relay.
Someone would need to figure out if you are lacking spark to the plugs or fuel pressure when it fails to start, then track down why.

Did you take the distributor cap off and see if it has moisture inside ?

the high humidity (water) is attacking your electrical starting system, whens the last time you changed your spark plug wires , distributor cap & rotor ? how about your fuel & air filters ? cleaned your battery terminals ? try it , it will help !!!!!!!!!

Could be moisture in the distributor cap.
I am assuming you mean it cranks but will not start.

Had the same issue with our 1999 chevy astro van, would crank but would not start. It had been raining and windshield had a leak, after 2 days of no rain it started. Pulled codes and was the Security system in the ignition switch. Hope this helps.

Hi, the most common reason for a car not starting in the rain is found in the spark plugs. Wire insulation can wear thin and this causes the voltage to arc to the metal of the car engine rather then going into the spark plug. You can check for this visually by opening the hood when it's wet outside and trying to start the car. You might be able to see an arc from the spark plug wires. Secondly check the distributor cap. Take a good physical examination of your distributor cap for any signs of a cracks. Also remove the distributor cap and check the inside of it for moisture. If you find any, wipe it clean; it won't work while wet.

you don`t say but it sounds like the moisture from the rain is sitting on the plug wires causing them to short the voltage to ground and possibly moisture in the distributor cap.how long has it been since a tune-up was done to the van.

check to see if the cover over the fuses and relays under the hood is tight

change plug wires moisture gets into them ive had the same problem cap and rotor