As of Thursday morning, 23 U.S. states are under air quality alerts from the Midwest to parts of the South and into the Northeast where wildfire smoke from neighboring Canada is creating hazy skies.

The worst-affected areas are currently from Wisconsin down to Tennessee and up to Virginia and even parts of Pennsylvania.

As the day develops, plumes of smoke are expected to linger over the Great Lakes, the Ohio Valley and into the Appalachian Mountains. Some smoke might even make its way into the Mid-Atlantic and parts of New Jersey.

New York City will be largely spared from the heaviest smoke. An air quality alert was issued there only as a precaution. Most of the day will be sunny with perhaps a touch of haze due to the smoke nearby.

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.'"

The latest round of unhealthy air quality due to smoke from wildfires in Canada has pushed into the United States, and it's ability to concentrate over areas from Wisconsin to Kentucky is aided by recent storms that spawned tornadoes, large hail and [damaging winds]).

Winds at the mid-levels of the atmosphere are causing the Canadian wildfire smoke to concentrate over a specific area of the midwestern and eastern U.S.

Meanwhile, a heat dome that’s been causing stagnant deadly heat in the Deep South for weeks is keeping the smoke largely out of the region.

The next round of widespread showers and thunderstorms for this area of the eastern Midwest and the East is forecast to arrive on Friday and continue through the weekend, which will clear the smoke.

But as long as the wildfires continue to rage in Canada, these events of dense smoke plumes will likely continue to disperse into the U.S. Canada's wildfire activity typically peaks from June to August.