That’s where I’ve mostly experienced it. Guess it could be anywhere though.
Terrifying. Pea soup, and people still going full speed and big-rigs in the mix.

im glad i am up here . eek. but we sometimes get it when the marine layer is above 5000 k feet. foooo of.

There were times when the whole country would be clear of clouds in satellite photos, but the CA Central Valley was socked in with low clouds and haze...no rain...just enough to block the sun. I haven't seen that kind of weather in recent years though. I read an article about a study and was surprised to learn they determined that less fog was the result of cleaner air, less air pollution from agriculture and cars.

Back in the 80's they actually were burning off the rice fields after harvest which put tons of smoke in the valley. They said the fog forms because of the particulates in the air combined with temp and humidity. I think the tullee fog is different, which is thick and low to the ground, but I think we are getting less of that kind also.

you are partialy correct in your statment as per wikipedia article below.
https://en.wikipedia.org/wiki/Tule_fog