CHICAGO (CBS) — Dense morning fog is impacting the commute in the Chicago area Monday morning but will give way to a warm, sunny day.

There is a dense fog advisory, especially north and west of Chicago. the advisory is in place through 9 a.m.

Visibility in those areas, including McHenry County, Dekalb and Rockford, could drop as low as less than a quarter of a mile or of less than 200 feet. Flights in the area were also affected.

As the fog clears out, the other big story of the day is the heat. With a high of 85 on the last day of September, the temperature is more like what the area would feel in the middle of summer.

Monday is the only day without a rain chance. Scattered showers and storms begin again Tuesday.