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

The Canadian wildfire smoke drifting into the United States is expected to largely dissipate by the weekend.

By Friday morning, the smoke is forecast to linger in the eastern Great Lakes from Detroit to Ohio, Pennsylvania, western New York state, down to Virginia and the Carolinas.

New York City is not expected to see much smoke, but skies over the Big Apple could still be a bit hazy due to the nearby plumes.

By Friday evening, the smoke will really begin to diminish in the East with lingering effects from New York to the Carolinas.

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