In many cities of East and Central China, air-raid shelters have a new function: sheltering residents from the ongoing heat wave.

Residents enjoy the coolness in an air-raid shelter near Wushan Square in Hangzhou, Zhejiang province, on Monday. [China Daily]?

Cities such as Hangzhou, Hefei, Luoyang and Nanjing have opened their underground shelters to the public for free, as some residents who cannot afford air conditioning, including retirees, students on summer breaks, and migrant workers and their families, seek shelter from the heat.

The Beijing-based National Meteorological Center reported that the heat wave will continue to scorch many parts of China in the coming two days.

The provinces of Hunan, Hubei, Jiangxi, Zhejiang, Fujian, Guangdong and Sichuan are sweltering in temperatures higher than 35 C, with the mercury possibly hitting above 37 C in some regions.

Outdoor activities should be avoided at high-temperature periods such as the early afternoon, and residents were advised to take necessary sunstroke prevention measures, the center said on Monday.

Many cities opened their air-defense projects to residents after equipping them with necessary service facilities and even arranging folk-art performances to entertain the guests.

Across China, hundreds of thousands of bomb shelters were built in the 1960s and 1970s as a defense against possible Soviet air raids. Many have since been torn down to make way for the cities' sprawling subway networks, while others were used as storage areas or parking lots, or rented out by governments.

In Hangzhou, capital of East China's Zhejiang province, 10 such projects with a combined area of 5,000 square meters have opened for free since July 1. It is the 10th year for the city to use its bomb shelters as summer resorts, and the shelters have been equipped with benches, tables, drinking water, TV and wireless Internet.

Yu Zhuya, 60, a retired bus company worker, was seeking shelter in one of Hangzhou's largest underground space near Wushan Square on Monday.

The shelter, hosting about 500 residents during the day on Monday, has a story height of 3 meters and is illuminated by efficient light bulbs.

"It has been my habit to visit the shelter during summer," said Yu, who would bring her lunchbox and stay in the shelter for 12 hours a day.

"It's a comfortable place to read newspapers, play cards and watch TV, and management staff are friendly to everyone," she added.

Sun Guilin, 69, a retired worker in Hangzhou, said the biggest attraction of the space is its tidy environment, cool temperature and convenient facilities. "There is free drinking water, and necessities are sold at small shops," she added.

Chen Feng, manager of the shelter, said up to 800 people will use the space as an entertainment venue on weekends, but some could be turned away by its noisy environment.

Across Hangzhou, the shelters are popular among the society's disadvantaged group, and will accommodate up to 5,000 residents a day, according to Cheng Zhiguo, director of a task force formed by the Hangzhou government to handle heat-stroke prevention issues.

Cheng told China Daily that the shelters have taken special measures to protect senior residents who are sensitive to the temperature's fluctuation.

"We request senior citizens to bring spare clothes and go out of the shelter for a break every two hours," he said.

Emergency plans are prepared at each underground shelter. Common medicines are also in place.

In Nanjing, capital of East China's Jiangsu province, 11 underground spaces have been opened to the public until Sept 10. With a permanent temperature of 20 C, the resorts open to everyone between 9:30 am and 5 pm every day and are cleaned and managed by designated staff.

In a bomb shelter near Nanjing's Wangjinshi, the space remains tidy with two dehumidifiers applied to keep it comfortable for the patrons. But gambling, dining and dances are banned there.

Luoyang, in Central China's Henan province, opened 18 underground resorts close to the downtown area and residential communities this year, all of them reinforced. Officials said they were glad to put these idle spaces to use.

But not all the cities in East China have underground resources to benefit the public.

In Shanghai, a city with more than 20 million residents, almost no free underground spaces could be used because of ownership issues or their poor condition from lack of maintenance, government officials said.

"Most of the air-defense works owned by the local government are the early projects that are humid and unsuitable for residents to stay long," said Cheng Ji, director of the civil defense office in the city's Xuhui district.

Most of them are built using the vulnerable bricks-and-tiles structure, he said. Only a small portion of them could serve as summer resorts but they have been used as storage facilities.

Some new underground spaces are run by developers, and the government has no right to open them for public use, he added.

In Shanghai's Huangpu district, most of the bomb shelters have been used as warehouses.

Apart from offering an alternative for residents to escape the heat, the opening of the underground shelters helps preserve the environment and partly relieves the power shortage in the peak season of summer.

In Hangzhou, where power rationing could be adopted at some communities in summer, free public underground resorts in 2010 conserved at least 480,000 kilowatt-hours of electricity and reduced carbon dioxide emissions by 478 tons.