People wear protective masks as the Roosevelt Island Tram crosses the East River while haze and smoke from the Canadian wildfires shroud the Manhattan skyline in New York City on June 7.

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CNN  — 

A whopping 75 million people from the Midwest to the Northeast and down to the mid-Atlantic are looking at an unhealthy smoky haze slowly drifting down from Canada.

New York, Philadelphia and other cities issued “code red” air quality alerts, urging everyone, but especially those at risk for respiratory issues, to stay inside and avoid the potentially noxious air.

New Yorkers unused to such pollution are living in the city with the worst air quality in the world as of Wednesday afternoon, although the rankings on air quality tracker fluctuate.

On Wednesday, you could barely make out the New York City skyline, and the air quality hasn’t been this bad since the 1960s.

The Federal Aviation Administration put a ground stop for flights bound for LaGuardia Airport in New York for part of Wednesday, delayed flights to Newark Liberty International Airport in New Jersey and warned of the potential flight delays throughout the Northeast corridor.

Schools and activities are being canceled in an effort to protect those most at risk.

And there’s not much anyone can do about it.

Smoke creeping down from the Quebec wildfires is going to continue, turning the sky an eerie orange along with it.

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How long will this last?

“This could be something we deal with off and on throughout the remainder of the summer,” CNN meteorologist Jennifer Gray said on “CNN News Central” Wednesday. “Canada is still early in their fire season, and it has just exploded; while some days might be better than others, this could be a problem we’re talking about long term.”

New York City’s Emergency Management Commissioner Zachary Iscol warned the city’s health advisory is expected to be a “multiple-day event.”

Why is it happening?

We are essentially stuck in a weather pattern, said Gray, pointing to an area of high pressure to the northwest of the Great Lakes.

“It’s channeling these winds out of the north and bringing the smoke in day after day,” she said. “Until this big weather pattern decides to shift and we get a change in wind direction, the smoke is going to stick around.”

The smoke could also move more toward the Midwest and the Ohio Valley before swinging back toward the Northeast and mid-Atlantic.

Why is this happening in the East this year?

The North American West has become much more accustomed to wildfire smoke in recent years. Last year, it was Europe suffering. This year, smoke is hurting the East Coast.

While this year could be relatively quiet for the Southwest, the National Interagency Fire Center predicts above normal fire activity in the Pacific Northwest through September and in the Northeast through August.

Of course, there’s a climate change tie-in. Here’s a key line from CNN’s report on the smoke: