Air quality in the northeastern U.S. remains unhealthy, although it improves slightly in New York

By Phil Helsel - NBC News

The air quality in the northeast of the United States continues to be unhealthy due to the wave of fires registered in Canada, which has created a thick cloud of smoke that in recent days has covered cities such as Washington D.C. or New York.

New York City had been covered in a creepy orange haze that began Tuesday as smoke from wildfires in Canada was blown south.

The city of more than eight million people had been considered the world's worst air quality this week, but as of early Friday it was ranked 15th on a list by the IQAir.com tracking service.

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Air quality alerts covered most of New York state, as well as Connecticut, New Jersey, all of Pennsylvania and Indiana, and parts of Ohio and Michigan, according to the National Weather Service.

"Looking ahead to the start of the weekend, smoke from near-surface wildfires associated with the Canadian fires is expected to continue to plague regions from the Great Lakes to the Mid-Atlantic with reduced air quality," the weather service said in a discussion of Friday's forecast.

A man stops to watch the smoke and haze envelop the One World Trade Center building in New York, Wednesday, June 7, 2023.J. David Ake / AP

However, he said that while a northwesterly flow around a low pressure system over the northeast would "continue the flow of smoke over the region," it was expected to "relax and eventually shift to more than one westerly direction on Saturday."

New York Mayor Eric Adams had warned vulnerable New Yorkers to stay home and everyone else to limit their time outdoors amid smoke. The weather service said an air quality alert extends through Friday for much of the area.

Other cities, such as Philadelphia and Washington, D.C., were also affected. Flights were also delayed or cancelled due to conditions.

Philadelphia schools were supposed to operate remotely Friday as a precaution, the city's school district said.

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New York public school students scheduled to attend class on Friday were also moved remotely, though a previously scheduled "administrative day" meant some students would not have attended class on Friday anyway.

More than 400 wildfires are burning in Canada, which is experiencing very hot temperatures and dry conditions, according to the Canadian government and U.S. meteorologists.

The United States and other countries have sent or promised to send firefighters or other aid to Canada.