CHICAGO — The greater Chicago metropolitan area is under an active Air Quality Alert this week after the Illinois Environmental Protection Agency declared an Air Pollution Action Day, warning that ground-level ozone has reached concentrations categorized as "Unhealthy for Sensitive Groups." The alert, issued by the National Weather Service in coordination with the Illinois EPA, affects nearly 9.4 million people across Cook, DuPage, Lake, McHenry, Kane, Kendall, Grundy, and Will counties — and a parallel alert was simultaneously issued for Northwest Indiana.
According to the National Weather Service Chicago, "Air quality is expected to be at unhealthy levels for sensitive groups. Consider limiting prolonged outdoor activity." The alert, which extended through Wednesday night, May 28, 2026, comes at a time when stagnant weather patterns — hot temperatures, low winds, and intense sunlight — are "cooking" pollutants emitted by vehicles and industry into a dense layer of smog hanging over the Chicago skyline.
