You need to replace the Distributor cap with a factory GM cap.
be sure to check the coil wire where it goes into the coil, pull it out and it should be shiney on the end. If not replace coil and wire too. That will fix it.
it could be the window
Distributer drawing moisture
why does your 85 Chevy give you problems when it rains
No, they cause floods
It could be a door seal or more likely the windshield is leaking.
you could do the prom inside if it rains outside!
heavy rains
Cause it does
cause it rains
Stationary fronts
it rains
The cause of an oak tree to foam when it rains is a bacterial infection living in the plants tissue. This can also be caused by a slime flux on the tree.