Stab in the dark: Maybe it has to do with the temperature of the asphalt surface? It stays warm because cars drive over it, and it heats the air above it. The warmed air rises, and pushes the fog up a bit? Just an educated guess.

Fog is amazing. I have never experienced fog like in Newfoundland. The other night, I was at my Taekwondo class. The school is up a hill, and has windows so you could see the fog rolling in from the sea towards town. I got in my car and drove home, descending into the ever-thickening fog. When I got home, everything was obscured. You could see our neighbours immediately nearby, but not much else. Generally we have quite a view.

It gets so humid here, while still cold. On really humid days, the carpet is damp, and the CAT gets damp. She's my little furry hygrometer!