A foggy morning can be a beautiful time to travel the Going to the Sun Highway in Glacier National Park.  Just make sure that the driver keeps his or her eyes on the road.  The amazing sights can be distracting, but the road is twisty, narrow, and travels along the edge of cliffs much of the time.  Having said that, I have to admit is is HARD not to look, so a trustworthy companion who is good with a camera is essential.  The fog looks like it's flowing into the valley like a river.