The National Weather Service in Sacramento has issued a dense fog advisory until 10 a.m. Tuesday for the central and southern Sacramento Valley, the delta and Northern San Joaquin Valley.
The advisory means visibilities will frequently be reduced to less than one quarter mile.
The weather service says if you're driving into thick fog you should slow down, use your low-beam headlines and leave plenty of distance between you and the car ahead of you.
Some slowdown in traffic has been reported around the valley due to the fog.
-Capital Public Radio Staff