Updated Air Quality Alert continues in effect Friday for a good portion of the Chicago area

The Illinois Environmental Protection Agency has extended the Air Quality Alert  for the Greater Chicago Metropolitan Area, including the northeast Illinois counties (grey-shaded on the highlighted map) from Midnight Thursday night until Midnight Friday night.

An air pollution action day is declared when weather conditions are
such that widespread ozone and or particulate levels are expected to
be at or above the unhealthy for sensitive groups category of the
air quality index.

Active children and adults especially people with pulmonary or
respiratory disease such as asthma should limit prolonged outdoor
activity.