Motorists on roadways along the coast and in the western valleys were advised to use extra caution because of the thick marine layer blanketing parts of San Diego County.
As of 7:45 a.m., the Federal Aviation Administration reported that flights arriving at Lindbergh Field were being delayed up to 45 minutes because of the low fog and the delays could increase.
A National Weather Service dense fog advisory for coastal and valley areas of San Diego County is set to remain in effect until 10 a.m. Thursday. Included under the advisory are the entire San Diego County coastline, and the cities of Escondido, Poway and Santee.
Forecasters said travel on Interstates 5, 8, 15 and 805 and on state Routes 52, 56, 67, 78, 94 and 163 could be affected during the morning commute. Visibility could be reduced to a quarter-mile at times.
“A shallow marine layer will continue to create areas of dense fog along the coastal plain and into the far western portions of the San Diego County valleys though about 8 a.m.,'' according to the weather service.
Drivers were urged to slow down, use low beams and leave plenty of distance in front of them.
Forecasters said more dense fog could roll into areas up to 10 miles inland again tonight into Friday morning.