CHICAGO (AP) — The U.S. Environmental Protection Agency posted air quality alerts for several states stretching from Montana to Ohio on Sunday because of smoke blowing in from Canadian wildfires.

“Air Quality alerts are in place for much of the Great Lakes, Midwest, and northern High Plains,” the National Weather Service said. “This is due to the lingering thick concentration of Canadian wildfire smoke over these regions. While the concentration of smoke in the atmosphere should begin to wain by Monday, there is still enough smoke to support unhealthy air quality that is unhealthy for sensitive groups in parts of these regions into the start of the upcoming week.”

The U.S. EPA’s AirNow air quality page rated the air in Chicago as “unhealthy” as of 9 a.m. CDT Sunday. And in Michigan, state environmental officials said the air “is unhealthy for sensitive groups.”

As of 12 p.m. CDT Sunday, AirNow shows portions of Montana, Wyoming, Colorado, North Dakota, South Dakota, Nebraska, Kansas, Missouri, Oklahoma, Arkansas, Minnesota, Wisconsin, Michigan, Ohio, Kentucky, and Tennessee, as well as all of Iowa and Illinois, are blanketed by poor air.

The Michigan Department of Health and Human Services advised people in the state to check the Air Quality Index regularly to decide if they should be participating in outdoor activities.

The Indianapolis Office of Sustainability issued a Knozone Action Day for Sunday, saying people throughout central Indiana should avoid time spent outdoors as much as possible, especially active children, the elderly, anyone who is pregnant, and those with asthma, COPD (chronic obstructive pulmonary disease), emphysema, heart disease or COVID-19.

Sensitive groups should remain indoors Sunday and refrain from activities that degrade indoor air quality, including burning candles and vacuuming.

Health officials have recommended people can stay safe by taking steps such as wearing a mask, staying indoors and keeping indoor air clean.