For those outside of California or the US, the San Joaquin valley lies in the center of California -- south of Sacramento to north-east of LA -- a very large portion of the state. Typically rural and filled with farms, ranches or oil wells, it is also the home of larger cities such as Fresno and Bakersfield.
In the summer it is hot hot hot. In the winter is cold and chilly and foggy. Seriously foggy. Dangerously foggy.
This type of fog is called Tule fog -- pronounce toolie fog -- and is the type that makes driving very difficult. Oftentimes you can't see 20 feet in front of you, so you can imagine.
Cars often honk at intersections to let other cars know that they are approaching. 20-car pile ups are not uncommon.