Intense Canadian wildfires are blanketing the northeastern United States in a dystopian haze, turning the air acrid, the sky yellowish gray and prompting warnings for vulnerable populations to stay inside.

The effects of hundreds of wildfires burning across the western provinces to Quebec could be felt as far away as New York City and New England, blotting out skylines and irritating throats.

American authorities issued air quality alerts. Hazy conditions and smoke from the wildfires were reported across the Great Lakes region to Buffalo from Cleveland.

A smoky haze that hung over New York City much of the day Tuesday thickened in the late afternoon, obscuring views of New Jersey across the Hudson River and making the setting sun look like a reddish orb. In the Philadelphia area, dusk brought more of a lavender haze.

Sal and Lilly Murphy, of Brooklyn, likened the burning scent to a campfire. They said they could even smell the smoke indoors, at a Manhattan restaurant, then walked outside and saw a sky that looked like it was about to storm — but was rainless. Ms. Murphy wore a mask for protection.

“It’s a little scary,” Mr. Murphy said.

Smoke from the fires has wafted through northeastern states for weeks now, but it’s only recently been noticeable in most places.

Governor Hochul said Tuesday’s hazy skies “were hard to miss,” and Mayor Adams encouraged residents to limit outdoor activities ”to the absolute necessities.”

The Quebec-area fires are big and relatively close, about 500 to 600 miles away from Rhode Island. 

A National Weather Service meteorologist based at Upton, Long Island, Jay Engle, said the wind trajectory that allowed smoke and hazy conditions to be seen across the New York City area could continue for the next few days. 

The main driver of conditions is the fires themselves. If they diminish, the haze would too.