Wildfire smoke from Canada and plumes of desert dust from the Sahara hovered over large portions of the United States on Wednesday, creating hazy skies and hazardous air quality from the Northeast to the Southeast.

The National Weather Service issued air quality alerts Wednesday for New York City and many surrounding areas, including New Jersey and most of Connecticut. Officials said those more sensitive to air pollution should limit their time outdoors and watch for respiratory symptoms from 11 a.m. to 11 p.m.

The U.S. Environmental Protection Agency warns that wildfire smoke contains dangerous pollutants in the form of fine particles known as PM 2.5 that can penetrate deep into the lungs and enter the bloodstream. Short-term exposure can lead to bronchitis, worsen asthma and create other health issues.

Despite those risks, people flocked to Madison Square Park in New York City on Wednesday afternoon, sprawling on the lawn in swimsuits and having lunch at picnic tables. More than a few business meetings seemed to have migrated to picnic benches in the shade.

When people were asked about the air quality, most answered with some version of “Huh?”

“It’s beautiful outside,” said Leonardo Hauschld, who was visiting from southern Brazil.

Some who had heard about the air quality said they couldn’t resist the sunshine and temperatures that reached the mid-80s.

Berit Adelaide, who is from Long Island, took her lunch break in the park even after chatting with a colleague about the air quality. “I still decided to get myself out to get some sunshine,” she said, “but I do see the haze in the air.”

Several air quality warnings were also in effect in western Canada for areas around the fires in that part of the country, with smoke billowing toward northwestern Ontario.

The smoke from the Canadian wildfires moved south and passed over the Midwest on Tuesday. Air quality alerts remained in effect Wednesday across Minnesota, Iowa, Wisconsin, Michigan and Ohio.

“We’ve definitely had it worse before,” Patrick Chavez, a founder of the Buena Tierra Run Club in Milwaukee, said Wednesday. Last week, he said, he could smell smoke during one of his runs.

As a leader of a running group, he takes the air quality warnings seriously.

“We don’t always cancel for air quality issues but we do share warnings for those that do have asthma, to carry their inhalers and maybe refrain from working out that day,” he said. (Members of Chavez’s group are used to dealing with extreme weather. He recalled one run when the wind chill put the temperature at minus 29 degrees.