CHICAGO (CBS) — Winter officially begins later Wednesday, but the Chicago area has a thick soup of fog in lieu of the usual snow and bitter winds.

The National Weather Service has issued a dense fog advisory until 10 a.m. for all Chicago area counties except for those that touch the Wisconsin state line. The advisory also affects much of Indiana and southern Michigan, east all the way to the Detroit area.

Visibility has been reduced to a quarter mile or less in some areas, particularly south of the Eisenhower Expressway and the Ronald Reagan Memorial Tollway.

The fog will dissipate through the morning as precipitation moves in, but visibility will be limited to a few miles until the early afternoon, according to the National Weather Service.

Motorists are advised to drive slowly and cautiously, keep headlights on, and leave plenty of distance ahead of their cars.

No flight delays were reported at O’Hare or Midway international airport.

CBS 2 Meteorologist Megan Glaros says a system producing light snow mixed with rain is moving eastward toward the Chicago area, but given the warm temperatures Wednesday, only light rain is expected once the system reaches Chicago.

The forecast high for Wednesday is 45 degrees, even though winter officially arrives at 11:30 p.m.

A couple of bursts of snow may be coming on Thursday, but Glaros says no accumulation is likely. The highs will drop through the rest of the week, topping out at 33 on Christmas Day.

Watch & Listen LIVE