Dense Fog Advisory issued for parts of the Chicago area – NBC Chicago

The National Weather Service has issued a dense fog advisory for a wide swath of Illinois with limited visibility and hazardous driving conditions.

The warning is valid until 9:00 a.m Monday in McHenry, DeKalb, Kane, DuPage, LaSalle, Kendall, Grundy and parts of Will and Cook counties, according to officials.

An earlier advisory had expired by noon, but fog is building again in some areas, with forecasters warning of visibility of a quarter of a mile or less during the evening and overnight hours.

According to the FAA, flights are delayed at least 15 minutes at Chicago’s O’Hare airport due to the fog, with more extensive delays in the evening hours.

The fog could cause dangerous driving conditions, officials warn.

During periods of heavy fog, motorists are encouraged to reduce speed, use low beams and increase the following distance on roads.

Using high beam headlights can cause additional glare in dense fog, making it difficult to see the road harder, according to the National Weather Service.