Spotty dense fog over northern portions of the Chicago area until pre-dawn hours Tuesday morning

A Dense Fog Advisory is in effect until 3AM CST for the northern Illinois counties adjacent to the Illinois-Wisconsin state line including Winnebago, Boone, McHenry and Lake Counties in northeast Illinois as well as Ogle, Lee, DeKalb and Kane Counties. Spotty visibility less than a quarter-mile, in some cases near zero will persist in these counties until early Tuesday morning, so if driving in these areas be alert to the possibility of quickly lowering visibility due to patchy dense fog.

Latest airport visibility in tenths of a mile…