Fog and Pollution Push Chicago Air Quality to Unhealthy for Sensitive Groups

At 6 a.m. on October 23, 2026, portions of the Chicago metropolitan area in Cook County and DuPage County recorded an AirNow.gov index reading of Level 3, which is categorized as “unhealthy for sensitive groups.”

The rating was driven by a combination of elevated pollutant levels and a dense fog advisory that remained in effect across the region.

AirNow.gov’s six‑tier index is used nationwide to inform the public about the health impacts of current atmospheric conditions.