When China’s leader Xi Jinping met with Communist Party delegates from Inner Mongolia last week, he urged them not to indulge in the struggle to improve the environment.

“We have to stick to the concept that clear water and green mountains are as good as mountains of gold and silver,” he said.

On Monday, large parts of China saw how bad the environment can still be.

The biggest and strongest dust storm in ten years swept over northern China, landed hundreds of flights, closed schools in some cities and threw a terrible shroud over tens of millions of people – from Xinjiang in the far west to the Bohai Sea, China’s weather service.

The storm that came after weeks of smog was reminiscent of the “air cupolaypses” the country routinely witnessed a few years ago, and forced the crash government’s efforts to address a political and public health crisis.

These efforts significantly improved air quality, especially in the capital. But this week, three forces – the post-Covid industrial boom, the ongoing effects of climate change on the deserts of northern China, and a late winter storm – together created a dangerous, suffocating pallor.

“Beijing is what an ecological crisis looks like,” wrote Li Shuo, the political director of Greenpeace China, on Twitter.

In an interview, Mr. Li said Monday’s storm was “the result of land and environmental degradation in the north and west of Beijing.” He added that Beijing’s industrial pollutants so far this year have exceeded the annual average for the past four years.

The dust was kicked up by a snow-capped thunderstorm that moved through Mongolia over the weekend. The storm there toppled electric towers, turned off power in several regions, and killed at least nine people.

The effects were felt in most parts of northern China. The Air Quality Index measurements set by the U.S. Environmental Protection Agency exceeded the hazard level for particles associated with sand and dust in the air. The pollutants, measured by the concentration of PM2.5, or particles of a size that is considered particularly harmful, were also dangerously high.

In Beijing, authorities ordered children, the elderly, and the sick to stay indoors – and everyone else to avoid unnecessary outdoor activities. The pollution, which turned the air yellow-orange in the morning and a soupy gray in the afternoon, was supposed to last until Tuesday morning.

Many residents responded with dark humor.

One meme that circulated online enhanced an image of the legendary headquarters of the Chinese state television broadcaster with a still image from Blade Runner 2049, the 2017 dystopian science fiction film. Another showed spaceships and characters from “Ultraman,” a Japanese Superhero franchise that marched through Beijing’s darkness.

With the improvement in air quality in recent years, newcomers to Beijing experienced such air for the first time.

“I couldn’t see the building across the street,” said Wang Wei, a 23-year-old college graduate who recently moved to Beijing from Henan, a province in central China. “I didn’t think the sky could be that yellow.”

The environment remains a politically sensitive issue for the leadership of the Communist Party. Mr. Xi has repeatedly called for a “green revolution” in China’s economy and last year pledged that China would accelerate efforts to reduce carbon emissions that have contributed to climate change.

However, pollution has proven to be a detrimental challenge as officials continue to prioritize economic development.

Recently completed legislative sessions took place during several days of heavy pollution due to increasing steel and cement production. Many environmental groups were disappointed that the new five-year development plan adopted at these meetings in Beijing did not include more specific government proposals to tackle climate change.

Even so, at times, Mr. Xi’s admonitions seem to induce the officials to act. Last week, the Ministry of Ecology and Environment warned authorities in Tangshan, the country’s steel production center in Hubei Province, after it was discovered that four steel mills failed to cut production to reduce pollution.

In Inner Mongolia, whose delegate met Mr. Xi in Beijing, the regional edition of The People’s Daily included an article on efforts to combat desertification that contributed to the dust storms. The article appeared on Monday as the worst pollution in years.

“Yellow sand is disappearing and green trees are thriving,” he proclaimed.

Albee Zhang and Elsie Chen contributed to the research.