story identification - Searching for a book involving blocks of fog

I read a book nearly twenty years ago when I was in Jr high. What I remember is a man traveling around with a teenage girl, (nothing twisted) in a camper I think, and there were these weird blocks of fog or mist. I believe there may have been a dog also. It was a novel in English. I believe it was written in the 70's or 80's. I remember a part in the book where two blocks of the fog got stuck right where a woman's house was. The man and girls stopped there for the night. I remember the girl didn't talk much. That's about all I can remember. I don't even remember the story behind what caused the fog and I really want to reread the book.

Answer

It's a long stretch, but it's possible you're thinking of Gordon R. Dickson's Time Storm

from one of the reviews on the Amazon link above:

    Gordon Dickson's "Time Storm", first published in 1977, is an excellent post-apocalyptic novel concerning the catastrophic after effects caused by on-going time storms (or time lines that appear as, and are called in the book, 'mistwalls') that continually sweep across sections of the Earth, as well as throughout the universe. As a time storm passes, a large swath of land becomes forever changed in time. A side effect is that for most of the population these time sweeps are deadly.
    Luckily (or you would have no story), a small percentage of the population (including a few animals) seem immune to the deadly effects of the time storms. The three main characters; the protagonist (Marc Despard), an autistic teenage girl (known as 'Girl'), and a leopard (called Sunday), are all richly defined.
    This story begins with the three unlikely partners traveling across country where they cross area after area that has been changed in time. The people (and/or creatures) that have been 'deposited' into the effected areas (if there are anyone at all), are either from some point in the future or from the past, but like any post-apocalyptic story, few are friendly. Even the survivors of his own time can be, and usually are, extremely dangerous.

Here's the intersection of two mistwalls (possibly your "blocks of fog or mist"):

Chapter 9:

    It did not take long to reach the end of it. I kept on a little further, however, not wanting to turn the corner until I could see behind it. But though we kept going further and further, we still did not seem to quite clear the end. Finally, I saw why. We were not going to be able to see behind that mistwall after all. Here at what I had thought was its point of termination, it had either bent to the right and continued, or run into another mistwall going off at an angle in that direction.
    At first, all I felt was disappointment that I was not going to get a look behind it. Then it occurred to me that perhaps the reason neither mistwall nor mistwall section had been moving had been because each had butted up against the other; and the two time change lines coming together had somehow created an unusual state or condition that had halted them both. The moment that I thought it, I was hungry to see what was behind the intersection of those two mistwalls.

There is, indeed a house behind the mistwall intersection, inhabited by a lone woman and her pack of trained dogs. The man, girl and leopard were on foot (on bicycles, actually; one of the few post-apocalypse stories where bikes are used) at this point in the story but in the beginning they were driving a panel truck.