LAHORE, Pakistan — In the vibrant Pakistani metropolis of Lahore, a city of 14 million people with a rich history and grand colonial-era buildings, evenings hold a special significance.

Markets thrum with activity, and families gather along bustling “food streets.” With the end of the year comes the height of the wedding season, when shimmering celebrations keep the city alive deep into the night.

But as a dense, suffocating smog has settled over Lahore’s skyline this month, the government has imposed restrictions that are reshaping the rhythms of a city that wakes late and thrives late.

Markets and wedding halls must now close by 8 p.m. Outdoor barbecues at restaurants are banned. Parks, zoos, historical monuments and museums are shut down. Complete weekend lockdowns — reminiscent of COVID-19 restrictions — are set to begin Friday.

“People here start shopping after 4 or 5 p.m. after men return from their jobs,” said Chaudhry Kabir Ahmed, a traders’ leader at the Ichhra market in Lahore. “Now the government is asking us to close by 8 p.m. It’s hard to change people’s habits so quickly. And if we open late, authorities raid us and impose heavy fines.”

Lahore, the capital of Punjab, the most populous province in Pakistan, regularly ranks among the world’s most polluted cities. According to IQAir, a Swiss climate monitoring group, Lahore has hit record smog levels in recent weeks, reaching a reading of 1,100 on the Air Quality Index on Nov. 14. Any level above 150 is classified as “unhealthy,” and anything over 300 is deemed “hazardous.”

Punjab province is next to north India, and both regions face alarmingly high levels of air pollution. On Monday, the AQI figure in the Indian capital, New Delhi, reached 1,785, and the city’s chief minister declared a “medical emergency.”

In Lahore, the concentration in the air of tiny particulate matter, which can penetrate deep into people’s lungs and even enter the bloodstream, has been nearly 100 times as high in recent weeks as the level deemed safe by the World Health Organization, said Christi Chester Schroeder, air quality science manager at IQAir.

Even outside the usual smog season that lasts roughly from November to January, when temperatures cool, the city’s air is polluted. Lahore has not had a day of “good” air quality, as measured by the AQI scale, since July 2021, Dr. Chester Schroeder said.

On Nov. 15, the provincial government declared smog a health crisis, saying that nearly 2 million people had already been sickened. Hospital hours have been extended, medicines for respiratory illnesses have been supplied and ambulances have been equipped with breathing equipment, said Marriyum Aurangzeb, a senior provincial minister.

UNICEF recently issued a stark warning about the extreme vulnerability of the more than 11 million children under the age of 5 in the province, citing their smaller lungs and lack of immunities.

Lahore’s emergency rooms are filled with patients — many of them children — suffering from ailments such as breathing difficulties, throat infections, persistent coughing and eye irritation.

“My 1-month-old child has been struggling to breathe,” said Sumaira, 25, who uses a single name, cradling her baby at Services Hospital. “I don’t know the exact cause, but I see countless children with similar problems. I can only pray for better weather.”

Ahmad Rafay Alam, a Lahore-based environmental lawyer, is one of a group of air quality experts who wrote a letter to Prime Minister Shehbaz Sharif urging the government to take immediate action.

Citing scientific studies, Alam said that about 45% of year-round air pollution in Lahore stems from tailpipe emissions, largely a result of low-quality fuel. Another 40% is attributed to industrial emissions and energy production.

The solutions to these problems, he said, “are neither cheap nor quick.”

The task of improving air quality cannot fall to just one country in the region, experts said. In 1998, South Asian nations, including Pakistan and India, signed the Malé Declaration, which aimed to address transnational air pollution together.

The effectiveness of that agreement, however, has been limited by funding shortages and a lack of political will. The issue gained renewed attention when the chief minister of Punjab province, Maryam Nawaz, recently called for “smog diplomacy” with India.

For most residents of Lahore, the smog has become a brutal presence, and the months of bad air are now referred to as the “fifth season.”

The poor face an even greater struggle. In a cramped house outside Lahore, just 7 miles from the Indian border, a 10-member family endures the choking air that seeps through cracked windows and unsealed doors.

“The air outside is thick and acrid, but there’s no escape indoors,” said Amna Bibi, 60, the matriarch of the family. She has watched the smog worsen each winter during her more than two decades in Lahore.

“Every year, it gets harder to breathe,” she said.

With schools across the city closed because of the hazardous air, children are either confined indoors or left to play in the streets, even though many already suffer from throat infections.

Families like Bibi’s in Lahore’s low-income neighborhoods can’t afford the protective measures, like air purifiers, that wealthier residents take for granted.

Some believe the smog is a sign of divine anger. During Friday Prayer last week, hundreds of thousands of Muslims across Punjab offered a special prayer for pollution-dampening rain, a ritual performed in times of calamity.

“Floods, smog, earthquakes — these are all signs of God’s wrath toward us,” said Syed Hashim, 23, a college student who attended the prayers. “It’s time to pray to God for forgiveness.”

In addition to vehicle and industrial emissions, the burning of rice stubble has long been identified as a major contributor to Lahore’s toxic winter air.

Many farmers say they are being unfairly scapegoated.

“Why waste so much time and money blaming us? Why not focus on the bigger polluters, like transport and industries?” asked Ghulam Mustafa, 41, a farmer in Lahore’s suburbs. “Instead, smog has ruined the quality of our crops, and now we need to spend more money to buy expensive chemicals to spray.”

The rapid growth of housing developments has brought brick kilns into Mustafa’s area to supply building materials, exacerbating the pollution.

Authorities have shut down many kilns, along with other polluting facilities like plastic-melting plants, for failing to comply with emissions control regulations.