They have that Tule fog, as it is called, in the central valley in California. A thick ground fog. I remember hearing of incredible pile ups on Hwy 5 during the season for it....no joke. A famous one involved 25 cars and twelve big rigs, and there were five fatalities, but the biggest was on Hwy 99 near Fresno. 108 passenger cars and 18 big rigs. The visibility can be zero. Sometimes combine that with freezing drizzle and black ice. You don't want to be there looking for a place to turn around..