The National Weather service has issued a dense fog advisory for the entire Chicago area until 9 a.m. Wednesday.
Visibility may sink to zero at times, but is expected to hover around a quarter mile, the weather service said.
The fog is expected to remain for part, if not all, of the Wednesday morning commute, the weather service added.
Drivers are advised to slow down, use headlights and leave plenty of distance between their vehicle and others.
