I think I have a belt issue but want to float it to the guru's.
1998 Discovery that screams like it's eating a cat in humid conditions...at the beach in NC or aroung Tennessee after a warm rain. Goes away after weather dries...belt dressing doesn't work.....

 

Sounds like a bad belt, pulley or belt tensioner, check them all.
Mike

 

Belt! Now she puurrrrrsssss again!

 

And you still do have a problem that will show up again soon.
Mike