New York air quality among world's worst due to California fires: Smoke hits Northeast

Wildfire smoke over eastern U.S. and Canada viewed from a satellite on June 6. Satellite image: CIRA/RAMMB

Air quality across the northeastern U.S. and Canada has plummeted to unhealthy levels due to smoke from wildfires burning from Yukon to Nova Scotia, which caused a thick haze in New York and many other cities.

Why it matters: Because of the smoke that drifted over Tuesday and other forms of air pollution, New York City, Detroit and Toronto had among the worst air quality of all cities around the world overnight.

Threat level: Air quality advisories were affecting up to 100 million people across the U.S. Tuesday, from the U.S. Northeast to the Midwest and Texas.

Driving the news: Canadian officials warned on Monday that the country is on pace to see one of its worst wildfire seasons on record from ongoing drought conditions and warming temperatures and for citizens to prepare for a long summer.

By the numbers: New York City ranked worst in the world for air pollution for much of Tuesday evening before Delhi, India, briefly overtook it overnight, according to IQAir, a Swiss air quality technology company. As of early Wednesday though, the American city retook the top spot.

Meanwhile, Canada, which is at its highest preparedness level for wildfires, saw at least nine new flare-ups on Tuesday.

Of note: In a typical year, wildfires in Quebec will have burnt 297 hectares (around 734 acres) around this time.

Thought bubble, via Axios' Andrew Freedman: The whole weather pattern lately has been extreme, with a massive heat dome roaming over Canada.

The big picture: In the U.S., at least 236 wildfires were actively burning on Monday, including eight large, uncontained fires, according to the National Interagency Fire Center.

What's next: Officials in the northeastern U.S., Midwest and Mid-Atlantic were warning of more poor air quality on Wednesday.

Go deeper ... Study: Increased wildfire risk could delay ozone layer's recovery

Editor's note: This article has been updated with new details throughout.