The National Weather Service extended a Dense Fog Advisory for North Texas until noon Tuesday.
NBC 5's Grant Johnson said visibility in most areas ranges from 1/2 mile to less than 1/4 mile. Visibility improved by late morning.
Officials urged North Texans to drive more slowly, use low-beam headlights and leave more distance between other drivers.
The latest news from around North Texas.
Tuesday’s heavy fog causes some major problems for those trying to fly in and out of Dallas-Fort Worth International Airport.
The FAA issued a traffic management program, including a ground stop for incoming airplanes, which caused about dozens of departure cancellations and inbound flights to be diverted to other airports. Delays are expected throughout the day at the airport.
As of noon, 139 flights had been cancelled and 157 more delayed in and out of D/FW International Airport. Dallas Love Field had 36 cancellations and 48 delays.
Most passengers we spoke did not have a problem with issues.
"We thought about it,” said passenger Ellen Nelms. “We thought about it being delayed, but my son didn't call us and he lives out here so I guess he figured they were taking off."
Many of the planes diverted this morning have already returned to the airport.
If you are flying out of the airport Tuesday you are asked to check ahead to make sure your flight is still on schedule.
Emergency Responders Cautious
Medstar spokesman Matt Zavadsky confirmed that their crews will not use lights and sirens when responding to emergency scenes because of the fog.
"Our goal is to get to the scene," he said. "Even if it takes a minute or two longer."
Zavadsky urged drivers to drive reasonably in the fog, including not making sudden movements and using blinkers.