Update 9:25AM CDT…
Visibility has improved area-wide by mid-morning – check visibility map below.
CHICAGO — Dense fog has developed across a good portion of the Chicago-area with visibility lowering to less than a quarter-mile to near zero in many areas.
A Dense Fog Advisory is in effect for much of northeast Illinois (grey-shaded counties in the headlined map). Until mid-morning (as late as 10am cdt) when visibility should be improved significantly.
If on the road, drive cautiously and be prepared to encounter spots where visibility lowers quickly to near zero.
Latest observed visibility in miles is displayed on the map below…