I immediately grabbed this prompt because I love the little poem of Carl Sandburg’s, Fog: 

The fog comes
on little cat feet.
It sits looking
over harbor and city
on silent haunches
and then moves on.
There’s a rational meteorological reason for fog — but it’s the stuff that so many illusions are made of. Fog shrouds a familiar landscape making it seem surreal, hiding the unknown, reshaping and blurring objects that are benign in the light.
When the fog is particularly heavy it seem as if one is on an island and what lies outside its bounds is uncharted territory. When I’m driving a car down a foggy road I feel like I’m in a foreign land able only to follow the curves of the edge and middle line to get to my destination — like a ship at sea surrounded by water. You look out from the deck but see little. You feel alone.
I remember standing on a beach in a heavy fog — a kind the Scots call a “haar”. About a half dozen of us had walked to the beach, but once there we spread out a bit, unable to see each other, it as as if the others had been swallowed up by “The Thing” or something else supernatural. Even though we could hear each other, we may as well all have been invisible.
Seeing fog set in is like watching a scary movie, you don’t want to feel apprehension, but at the same time there is something compelling in the unknown.