Residents of Chicago experienced reduced visibility Thursday morning due to dense fog enveloping the area, causing the National Weather Service to issue an advisory that warned of “sharply reduced visibility” with some regions seeing a quarter-mile view or less. This advisory impacted several Illinois counties including Lake, McHenry, DeKalb, Kane, DuPage, LaSalle, Kendall, and Kenosha County in Wisconsin, a situation detailed by the National Weather Service.