In the fall, night likes to hang on just a little bit longer and just a little bit colder then the previous night. The cold air combined with the warm water is a sure combination for fog and even some of your most traveled beats can become transformed into someplace new.
a foggy fall morning on the fox river (wisconsin)
Now, I wouldn't actually attest that fog can help fishing. To tell the truth, I don't have any memorable fish stories that I can recall while fishing in the clouds. But, it sure does give some other purpose to fishing other than just catching the fish; to be there when the familiar becomes foreign again.
a fox river smallmouth bass, wisconsin style
It also doesn't hurt the morning either when the fish bite after the fog burns off!