The Chicago Metro area and Northwest Indiana are under an air quality alert through Wednesday night, the National Weather Service has announced.
The Illinois Environmental Protection Agency declared an Air Pollution Action Day due to unhealthy ozone levels. Harmful ozone levels occur when pollution interacts with sunlight and produces smog, which is harmful to people with lung or heart disease, older adults, children and teenagers, according to the EPA.
An Air Quality Alert is in effect through Wednesday for the Chicago Metro and Northwest IN due to unhealthy ozone levels. Air quality is expected to be at unhealthy levels for sensitive groups. Consider limiting prolonged outdoor activity. #ILwx #INwx pic.twitter.com/G8kg5wNXKk
— NWS Chicago (@NWSChicago) May 26, 2026
The alert comes as Tuesday’s and Wednesday’s temperatures are expected to reach the low- to mid-80s, a bit warmer than average for the end of May, according to the weather service. Sensitive groups should consider limiting prolonged outdoor activity.
The EPA advises those with asthma to keep quick relief medicine handy during times of poor air quality.
Weater service meteorologist Mark Ratzer said the air quality can still be dangerous, even if the air does not look hazy.
“Ozone is just an odorless, colorless chemical, microscopic, that you don’t see in the air,” he said. “Whereas wildfire smoke would be more of a particulate, where there’s actually particles in the air that you can see.”