A Dense Fog Advisory is in effect until four am for Berks, Lehigh and Northampton Counties, according to the National Weather Service.
Visibility is less than one-quarter mile making for hazardous driving conditions.
If driving, slow down, use your headlights, and leave plenty of distance ahead of you.
Photo on I 78 near Summit Lawn in Allentown
Photo on Tilghman Street in Allentown