A dense fog advisory has been issued for McHenry County and the majority of the surrounding suburbs, according to the National Weather Service.
The advisory remains in effect until noon, with some areas not expected to see improvement until the early afternoon.
The dense fog is expected to make the morning commute for motorists very challenging, according to the weather service. Many areas are experiencing extraordinarily dense fog with visibility of less than 200 feet.
Conditions will gradually improve late this morning.