Wildfire smoke updates: CDC issues health alert on wildfire smoke exposure

Videos verified by ABC News show smoke from Canada's wildfires casting a haze over several U.S. cities on Wednesday.

One video, taken by a driver and posted on Twitter, shows the wildfire smoke hanging over a highway near Lawrenceburg, Indiana, as the state and much of the Midwest were under air quality alerts.

Lawrenceburg is located some 100 miles southeast of Indianapolis, near the state border with Ohio and Kentucky. The city is about 25 miles west of Cincinnati, Ohio.

-ABC News' Matthew Holroyd

Air quality alerts remain in effect for more than 100 million Americans across the Midwest and into the Northeast Wednesday evening, as wildfire smoke from neighboring Canada blankets large swaths of the United States.

Hard-hit Chicago, Detroit and Minneapolis remain among the top five places in the world with the worst air quality as of Wednesday evening.

The air quality alerts are mainly for people in sensitive groups who have upper respiratory issues.

The near-surface smoke is expected to stretch from Wisconsin to Kentucky and into the Carolinas Wednesday evening. Some of the smoke will likely make its way into the mid-Atlantic overnight. Pittsburgh to Syracuse are forecast to see hazy, smoky skies and poor air quality Wednesday night.

Through Thursday, the smoke is expected to move out of the Midwest and linger farther east but not be as heavy. No significant smoke issues are forecast at this time for major Northeast cities, including New York City.

-ABC News' Melissa Griffin

While the poor air quality is mostly hovering over the Midwest, the dangerous smoke is also drifting toward the East Coast.

New York Gov. Kathy Hochul has expanded Wednesday's air quality health advisory to include the entire state.

"Air in Western New York, Central New York, and the Eastern Lake Ontario regions is forecast to be 'Unhealthy,'" Hochul's office said. "The forecast for the remainder of the state, including New York City and Long Island, is 'Unhealthy for Sensitive Groups.'"

In Chicago, where the Air Quality Index is in the "very unhealthy" category, an Air Quality Alert is in effect until Wednesday night.

Chicago Mayor Brandon Johnson is urging "particularly sensitive populations, including individuals with heart or lung disease, older adults, pregnant people, and young children" to avoid outdoor activities.

Camps have been moved indoors where possible, the mayor said, and he's encouraging "Chicagoans without access to properly ventilated and safe indoor conditions" to "please utilize our public libraries, senior centers, Park District facilities, and the Cultural Center or the six community service centers that operate from 9am-5pm."