The Illinois Environmental Protection Agency has determined Tuesday will be an Ozone Action Day for the entire Chicago area including DuPage, Kane, Kendall, Grundy, Lake, McHenry and Will counties.
An air pollution action day is declared when ozone levels are expected to be unhealthy for sensitive groups, including people with pulmonary or respiratory disease.
"Those individuals need to stay hydrated," said James Martinez, American Lung Association. "They need to limit their activity outside. Those with elderly loved ones, or again, children with asthma, shouldn't leave them alone."
The American Lung Association also warns to keep pets out of cars on hot days.