A dense fog advisory was in effect early Monday in San Diego County's coastal areas, where visibility was down to a quarter-mile or less in places.
The National Weather Service issued the advisory until 9 a.m., saying areas within 10 miles of the coast were affected, including Interstate 5 and parts of Interstate 8, Interstate 15 and state Route 163.
"If driving, slow down, use low beam headlights and leave plenty of distance ahead of you," the weather service urged.
