The National Weather Service has issued a Dense Fog Advisory for the central valley and the western, lower portions of Calaveras and Tuolumne counties until 11 AM this morning.
Locations affected by the fog include both Stockton and Modesto and portions of Highway 99.
Motorists should be alert for areas of dense fog and be prepared to slow down when visibility drops.
A Dense Fog Advisory means visibilities will frequently be reduced to less than one quarter mile. If driving, slow down, use your headlights and leave plenty of distance ahead of you.