In the 1970s, the city of Nanjing built more than 1,000 bomb shelters, at a time when the country feared tensions with the Soviet Union would escalate into war.

Fifty years later, most of the shelters have been turned into underpasses, shopping malls, or libraries. But this week the surviving shelters became the city’s coolest underground hangspots as officials opened them to help residents escape a record-breaking heat wave.

Since mid-June, blistering heat has swept across more than half of China, affecting more than 900 million people, state media reported Friday citing data from the National Climate Center. Governments and residents are looking for any way to adapt to temperatures that have already caused at least two deaths.

Over the past month, 71 weather stations recorded their highest temperatures ever. Shanghai, the country’s most populous city, logged temperatures over 40 degrees Celsius (104 Fahrenheit) for three consecutive days Tuesday to Thursday, hitting 40.9 degrees Celsius on Wednesday, the city’s highest temperature since 1873.

The life-endangering hot weather has brought a surge of heat stroke cases across many cities since July. Sixth Tone’s sister publication The Paper reported that a 49-year-old factory worker in Zhejiang died on July 8 after he passed out in a warehouse and was in shock when sent to the hospital with a body temperature of nearly 41 degrees Celsius.

Li Zhao, a climate risk researcher at Greenpeace East Asia, told Sixth Tone the hot weather is part of a sustained heat wave across the northern hemisphere, another example of the threat posed by climate change.

“Since the 1990s, China has witnessed a significant increase in the number of days, frequency and extremity of heat waves in its major urban regions,” Li said. In addition to a public health crisis, Li warned that the heat has already strained the power grid and threatens industrial production.

The Nanjing civil defense office opened seven underground air-raid shelters in four districts on July 10. Equipped with cold drinks, Wi-Fi, televisions, newspapers, microwaves, and medical aid, the shelters offered a cool spot to wait out the heat. Some stayed open into the evening.

Zhao, a 58-year-old retiree who only gave his surname and visited one of the underground shelters near his residential compound Tuesday, told Sixth Tone the bunkers were popular with older people, and outdoor workers on noontime breaks.

“It’s a great place to refresh yourself in the summer, even if it gets a bit moist and noisy sometimes,” he said.

Many residents in Nanjing went to ice rinks or hid in public libraries to dodge the heat. Zhao, who moved to the city from the north a couple years ago, said he’s tried as much as possible not to step outside for fear of heat stroke. “It’s the hottest summer I’ve ever seen here,” he said.

It’s not an entirely original idea. Before the widespread use of air conditioning, residents of the “furnace city” of Chongqing regularly gathered in underground bomb shelters during the height of summer, even sleeping there when the nights were hot.

The relentless heat has been particularly hard on quarantine workers, who are outdoors in plastic hazmat suits for hours to manage China’s current strategy of continuous mass testing. Since last month, multiple cities have reported cases of heat stroke among community health workers, as videos widely circulated on social media showed community health workers wearing ice vests or ice popsicles as necklaces.

Jia, a virus testing worker in Shanghai’s Baoshan District who only gave her surname, told Sixth Tone the hardest part was dealing with overheated, testy patients lining up in the hot sun.

“I feel much luckier compared with my colleagues since I’ve got an air conditioner in the kiosk,” the 32-year-old said. “Some of them have to sit in the open air the whole morning or afternoon in a hazmat suit.”

The Ministry of Emergency Management has ordered all outdoor work to be halted when the temperature goes above 40 degrees Celsius, and prohibited overtime work outdoors above 35 degrees Celsius. On social media, images of traffic officers dressed in blue hazmat suits have set off heavy criticism and calls for enforcement.

Liu Li, an emergency physician at Renji Hospital in Shanghai, told state-owned Hong Kong newspaper Wen Wei Po that prolonged heat can damage internal organs. The death rate of a severe heat stroke could reach 40 to 50% on average since people, especially the elderly, tended to downplay the severity of the illness.

Companies are promising high-tech solutions. MBO, a global refrigerator equipment maker, said its Guangdong-based subsidiary has rolled out a wearable air conditioner on July 10. With an average weight of around 3.5 kilograms and price of 8,888 yuan ($1,314), the company claimed it could produce 16-degree air in three minutes and aims to keep outdoor workers cool amid the scorching summer heat.

Some relief may be coming, with the heat in China’s eastern regions expected to ease after July 18, Chen Tao, chief weather forecaster for the China Meteorological Administration, said in an interview with People’s Daily Thursday.

Regardless, the bomb shelters in Nanjing will stay open until the summer heat wanes in late August.

“It’s a surprising summer treat,” said a postgraduate student surnamed Yang who visited the shelter Sunday. “I felt like it saved my life — I was melting at a nearby temple before.”

Editor: David Cohen.

(Header image: A sanitation worker uses a towel for shade in Shanghai, July 13, 2022. VCG)