In nearly every corner of Karachi, there are signs of the heat wave scorching the sun-baked city.

Hundreds of patients suffering from heat-related illnesses pour into the hospitals every day, pushing them far past their capacity. Morgues overwhelmed by a surge in bodies are struggling to find space.

Frustrated residents have begun blocking roads with stones and sticks to protest shortages of electricity and drinking water. Even the usually bustling markets and streets have emptied as people avoid leaving their homes unless they must.

Karachi, Pakistan’s largest city and its economic hub, is the latest place to suffer as South Asia roasts under a blistering heat wave this summer, a brutal reminder of the deadly toll of climate change in a part of the world especially vulnerable to its effects, and in a country where ineffective governance and large economic disparities have magnified the sufferings of its poorest citizens.

In a particularly dire eight-day stretch late last month, temperatures reached 104 degrees Fahrenheit (40 degrees Celsius), with high humidity adding to the misery. That was the hottest since 2015, a year when officials reported that more than 1,200 people died from heat-related causes in Karachi.

With temperatures still hovering near 100 degrees Fahrenheit, the sense of crisis has persisted.

“It feels like living in a furnace,” said Akbar Ali, 52, a rickshaw driver who has transported many heat-struck people to the hospital in recent weeks. “It’s terrible seeing people collapse on the street.”

A port city on the Arabian Sea, Karachi is known for its hot summers and monsoon floods. Such extremes are particularly hard for the 60 percent of residents who live in the city’s sprawling slums, where houses are shoddily made of concrete or tarps, and roads are unpaved.

But this summer has been particularly bad. In the stretch of intense heat from June 23 to June 30, the city’s largest morgue received about three times as many bodies as it does on a typical day, according to the Edhi Foundation, a charity known for its extensive morgue operations and large ambulance fleet.

In all, the charity’s morgues received around 700 bodies in those eight days. Though the cause of death was not clear in every case, the timing was suggestive.

“This is a humanitarian crisis, but many heat wave-related deaths won’t be officially recorded as heat deaths,” said Erum Haider, an academic at the College of Wooster who has studied Karachi’s civic challenges. “They often get classified under ‘fever,’ ‘heart attack,’ or ‘infant mortality,’ which obscures the true impact.”

In recent weeks, power outages in the slums have become frequent and prolonged, lasting from six to 16 hours a day. Without power, millions cannot use the electric fans that offer some relief (air-conditioning is rare). Frustration with the power cuts has prompted residents to regularly block major roads in protest.

The outages are “catastrophic for everyone in these neighborhoods during a heat wave, but particularly for infants, the elderly and pregnant women,” Ms. Haider said.

Water has also become scarce. Many neighborhoods face severe water shortages, turning the lack of clean drinking water into a public health crisis. In Karachi, a significant portion of the population relies on purchasing water from private companies through tankers, as the city’s water infrastructure fails to meet the needs of all its residents. During the summer, even areas that typically receive piped water are compelled to buy water because of shortages. Skyrocketing prices for water tankers are adding to the burden of already struggling communities.

“The cost of water tankers has doubled or even tripled,” said Mehmood Siddiqui, a private-school teacher, whose monthly salary is $143. “They’re now charging $28 for a tanker of water that cost $14 just last month. It’s outrageous.”

Hospitals are overwhelmed with patients suffering from heatstroke and severe dehydration.

“Patients are reporting symptoms like high fever, weakness, gastroenteritis, vomiting and diarrhea in numbers far exceeding normal,” said Nasreen Gul, a nurse at Jinnah Postgraduate Medical Center, the city’s largest state-run hospital.

Government officials have sought to play down reports of large-scale heat wave fatalities. Karachi Commissioner Hassan Naqvi, citing data from government hospitals, suggested that the number of deaths related to the heat was minimal.

Government officials have established cooling centers across the city. Charitable organizations are also providing some relief to residents, setting up roadside camps to offer water misting as well as glasses of cool water or Rooh Afza, a popular summer beverage in South Asia.

Rain last Thursday brought relief to Karachi after the midday temperature peaked at 104 degrees Fahrenheit. But it highlighted the city’s vulnerability to the summer’s other major weather problem: devastating floods.

“We can pray for rain to cool the weather,” said Ali Afzal, 44, a car mechanic in Karachi whose house was demolished in the July 2022 urban flooding caused by heavy rains. “But more rain poses another challenge, especially for city residents ill prepared to handle it.”