The Indiana Department of Environmental Management has declared Wednesday to be an “Air Quality Action Day,” saying Northwest Indiana’s ozone levels are expected to be unhealthy for sensitive groups.

IDEM announced Tuesday that Northwest Indiana residents can expect continued high temperatures, modest humidity, light winds under mostly sunny skies, and Canadian wildfire smoke, according to a news release.

The Associated Press reported during the weekend that much of the upper Midwest was dealing with unhealthy air because of drifting smoke from Canadian wildfires. Manitoba declared a state of emergency because of the wildfires, leading 12,600 people to evacuate their homes.

The fires in Manitoba have burned more than 3,861 miles, according to the Associated Press.

“Air Quality Action Days” are declared based on the U.S. Air Quality Index, which is the Environmental Protection Agency’s tool for communicating about outdoor air quality and health, according to the EPA’s website.

Sensitive groups that could be impacted by poor air quality include people with heart and lung disease, older adults, children, people with diabetes and those with a lower socioeconomic status, according to the EPA’s website.

Ricky Castro, meteorologist in the National Weather Service’s Chicago office, said the “Air Quality Action Day” declaration was first sent because of lingering effects of the Canadian wildfires.

“If there were some lingering effects and some smoke aloft, that could be conducive for elevated ozone levels,” Castro said.

In addition to hazy skies, Castro said Northwest Indiana residents will notice more humid conditions and more stagnant air. Winds might pick up on Wednesday afternoon, Castro said.

“Usually on hot and humid days, it’s not uncommon to have elevated ozone levels and air quality alerts,” he added.

IDEM’s “Air Quality Action Day” lasts from midnight to 11:59 p.m. on Wednesday, according to the agency’s news release.

Castro expects a cold front to pass through Northwest Indiana on Thursday, which will help break the unhealthy ozone levels and air quality.

For those in sensitive groups, Castro recommends being mindful of time spent outdoors and to monitor their symptoms closely. He also recommends that people keep a close eye on infants and their behavior.

“Stay cool, stay hydrated,” Castro said. “But, in terms of some of the air quality issues, consider making outdoor activities shorter and less intense.”

mwilkins@chicagotribune.com