Southern California is getting a taste of fall weather, with spooky dense fog early in the week and howling Santa Ana winds picking up just in time for Halloween. A low, dense fog blanketed much of Southern California on Monday morning, bringing cool weather from Los Angeles to San Diego. In the San Diego region, the widespread fog decreased visibility to less than a quarter-mile and prompted the National Weather Service to issue a hazardous-driving warning. The fog, caused by a shallow marine layer and a lack of wind, was less widespread in the Los Angeles area but was thick along the county’s coast.