Dense fog could spread into Chicago area Monday morning: weather service

Dense fog is expected to sweep over the Chicago area Monday morning, according to the National Weather Service.

Areas of dense fog over northern Illinois will move south into Cook and DuPage counties, the weather service said in a hazardous weather outlook statement.

Visibility in the affected areas will be under a quarter mile, the weather service said. Drivers are advised to reduce speed, use low beams and allow extra travel time.

The foggy conditions are expected to improve by mid-morning, the weather service said.