GEOFF BENNETT: Welcome to the "NewsHour."

A heavy pall of polluted air still blankets much of the Eastern U.S. tonight.

It may not dissipate for days, as fires in Canada send vast curtains of smoke drifting south.

AMNA NAWAZ: The bad air has officials warning, in effect, that breathing can be hazardous to your health.

It's also scrambling schedules, from airports to schools to the White House.

Stephanie Sy has our report.

STEPHANIE SY: A huge swathe of the country spent another day shrouded in haze.

This morning, smoke still obscured parts of the Manhattan skyline.

JOHN CHAN, New York City Resident: The smoke obliterated the island yesterday.

So, it is obviously not a passing phase of wind changes, but it's serious pollution in the air.

STEPHANIE SY: As hundreds of wildfires rage out of control in Canada, winds have carried the smoke farther south, all the way to Raleigh, North Carolina, which woke up to hazy skies.

And in the nation's capital, a blanket of smoke lay over the White House, blurring the Washington Monument in the distance.

White House officials postponed today's outdoor Pride celebration until Saturday.

Millions of people were under hazardous air quality advisory today from the Northeast to the South and parts of the Midwest.

Authorities advised people to stay indoors, especially young children, the elderly, and those with respiratory issues.

Allergy and immunology specialist Dr. Purvi Parikh described the health risks.

DR. PURVI PARIKH, Allergy and Asthma Network: Wildfire smoke has particulate matter.

It's very, very small.

And that small particulate matter can really get lodged deep into your lungs.

So it can cause a lot more lung damage in the short term and long term.

And in addition to these particles, wildfire smoke has a variety of gases too that can be harmful to breathe in.

STEPHANIE SY: New York state is making a million N95 masks available to the public, including 400,000 for New York City.

MAN: Just want to make sure that we are being a safe as we can to protect our health.

STEPHANIE SY: The city's mayor, Eric Adams, has gone door to door disturbing masks to residents.

He says the worst of the air may be behind the city.

ERIC ADAMS (D), Mayor of New York: The smoke models are not indicating another large plume over the city, so there is a chance for significant improvement by tomorrow morning and throughout the day tomorrow.

STEPHANIE SY: Even so, New York City announced public schools will teach remotely tomorrow.

Meantime, poor visibility prompted the Federal Aviation Administration to cancel or delay flights into New York area airports and Philadelphia's international airport.

The dangerous air quality also canceled or postponed more sporting events, from racing at Belmont Park in New York to the Washington Nationals' home baseball game.

New Jersey Governor Phil Murphy says the harmful impact of the fires is further proof we must do more to tackle the climate crisis.

GOV.

PHIL MURPHY (D-NJ): Climate change is here.

And, unfortunately, this is our reality.

That disturbing orange haze in the sky, the smell of smoke and that burning in our throats, those are clear warning signs that the status quo cannot continue.

STEPHANIE SY: Paul Ullrich, a professor of regional climate modeling at U.C.

Davis, agrees.

PAUL ULLRICH, University of California, Davis: We are experiencing warmer conditions and more extremes every year.

We have some manifestation of that, whether it be an extreme tropical cyclone, an extreme wildfire, tornado outbreaks or other forms of extreme weather.

So the evidence is continuing to pile up that we are having a clear impact on the climate system, and, as a consequence, the climate system is having an impact on us.

STEPHANIE SY: With more than 400 wildfires still burning in Canada, forecasters worn the smoke could linger over the Eastern U.S. through the weekend.

For the "PBS NewsHour," I'm Stephanie Sy.