As South Asia bakes under a blistering heat wave, life-or-death decisions arrive with the midday sun.

Abideen Khan and his 10-year-old son need every penny of the $3.50 a day they can make molding mud into bricks at a kiln under the open sky in Jacobabad, a city in southern Pakistan. But as temperatures have soared as high as 126 degrees Fahrenheit, or 52 degrees Celsius, in recent days, they have been forced to stop at 1 p.m., cutting their earnings in half.

“This is how we survive,” said Mr. Khan, sweat dripping down his face and soaking through his worn clothes. “It’s a choice between working and collapsing from the heat.”

It is yet another brutal summer in the age of climate change, in a part of the world that is among the most vulnerable to its dire effects. And there is more suffering to come: The extreme heat that Pakistan and neighboring India have been experiencing will continue for days or weeks, forecasters say. Already, it has exacted a deadly toll.

In the northern Indian state of Bihar, officials said that at least 14 people had died from the heat. Reports from other states in India’s north indicate that the count could be considerably higher. In both India and Pakistan, hospitals have reported large numbers of heatstroke cases.

Ten of those who have died in Bihar were poll workers preparing for the voting to be held in the state on Saturday, the final day of India’s national election. To mitigate the heat, glucose and electrolytes are being distributed to polling officers, tents are being erected to provide shade and earthenware pots will provide cool water. New Delhi, where temperatures have approached 122 this week, nearly 20 degrees above normal, recorded its first official heat-related death of the year on Wednesday.

In Jacobabad, long regarded as one of the hottest places on Earth, the temperature reached 126 degrees on Sunday, with highs of 124 each of the following three days. About 75 miles away, the Pakistani town of Mohenjo Daro, notable for its Indus Valley Civilization sites from 2500 B.C., reached 127 degrees on Sunday, just shy of a record set in 2010.

“This isn’t heat,” Mr. Khan, the brick laborer, said. “It’s a punishment, maybe from God.”

The blazing temperatures compound the challenges for Pakistan, a country of 241 million people that is already grappling with economic and political turmoil.

For the more than one million people who live in the Jacobabad district, life is dominated by constant efforts to find ways to cope with the heat. Blackouts lasting 12 to 20 hours a day are common, and some villages lack electricity altogether. The absence of necessities like readily available water and proper housing exacerbates the suffering.

Most residents cannot afford air conditioning or alternatives, like Chinese-made solar power batteries and chargeable fans. A solar panel to run two fans and a lightbulb costs about a month’s wages for laborers in Jacobabad.

The water crisis is so severe that donkeys can be seen on the streets carrying tanks, from which residents buy enough water to fill five small plastic jerrycans for $1. Soaring demand has pushed up the price of ice, making this essential commodity even harder to find.

Many of the poor have no choice but to work outside. Rice, the lifeblood of Pakistan’s agriculture, demands backbreaking labor in the fields from May to July, the hottest months.

For Sahiba, a 25-year-old farmworker who uses one name, each day starts before dawn. She cooks for her family, then walks for miles with other women to reach the fields, where they toil until afternoon under the relentless sun. Nine months pregnant with her 10th child, she carries a double burden.

“If we take a day or half-day break, there’s no daily wage, which means my children go hungry that night,” Ms. Sahiba said.

Each summer, 25 to 30 percent of the district’s population becomes temporary climate refugees, according to community activists. Some seek refuge in Quetta, a city 185 miles north, where the heat is more bearable. Others go to the port city of Karachi, 310 miles south, which has had its own deadly heat waves but offers some relief with its less frequent blackouts.

“Those who can afford it may rent houses in cooler cities, but most residents are simply too poor. They struggle to survive under makeshift tents erected in the open sky,” said Jan Odhano, head of the Community Development Foundation, a Jacobabad-based organization that helps the poor cope with the heat.

Jansher Khoso, a 38-year-old garment worker, knows this struggle all too well.

In 2018, his mother went to the hospital with heatstroke as temperatures spiked in Jacobabad. Now, every April, he sends his family to Quetta, where they remain until the autumn, while he works in Karachi. But this comes at a steep price.

“I work for 16 hours in Karachi to afford the expense of this temporary migration,” Mr. Khoso said, “because I don’t want any of my family members to die in the cruel heat of Jacobabad.”

Jacobabad’s suffering has not been limited to high temperatures. In 2022, monsoon rains and devastating floods — linked to erratic weather patterns associated with climate change — submerged the district and about a third of Pakistan overall, killing at least 1,700 people.

The heat is nothing new in the city, which was named after John Jacob, a British brigadier general who experienced its harsh climate firsthand in the 19th century.

Leading a small force to quell rebel tribes and bandits, General Jacob lost a lieutenant and seven soldiers to the heat on the first day of a 10-mile march. His diary described the wind as “a blast from the furnace” even at night.

To cope with the hostile climate, General Jacob introduced an irrigation system and built three canals to supply fresh river water to residents. Today, the canals are dry and full of garbage.

Suhasini Raj contributed reporting from New Delhi.