While the white-sand beaches and five-star international resorts are meant to be the main attraction, for the hundreds of thousands of Chinese retirees who descend upon this tropical city every winter, dancing on the seaside promenade is often the real draw. On a recent, balmy morning, palm trees swayed along the beachfront promenade as gray-haired dancers twirled and sashayed about. Retired men in head-to-toe Hawaiian print and women in floppy hats and flowery skirts sat on wheelchairs and folding stools, exchanging gossip over card games. Nearby, singers took turns belting out Mao-era favorites on an outdoor karaoke machine. Nearly every corner of the promenade was occupied by older snowbirds looking to escape the dreary, bone-chilling winter of the north. And here, in this seaside city on Hainan island, the southernmost edge of China, was their wintertime paradise. Welcome to China’s Florida. “Oh, we absolutely love it here,” said Xu Yan, 70, sporting a dyed perm and big sunglasses as she sat beneath a palm tree near a gaggle of ballroom dancers. Splayed out on a pink towel next to Ms. Xu was her companion, a toothless white Chihuahua named Maomao, who was burying his snout into a mound of torn-up hot dog pieces. Every winter for the past 13 years, Ms. Xu, a retired airline worker, and Maomao have left their home in the frigid northeastern city of Harbin to stay in Sanya. Like Ms. Xu and Maomao, more than half of the nearly 400,000 retired snowbirds who flock to Sanya every year are said to hail from China’s northeast. China’s population is rapidly aging; experts predict that by 2055, 400 million Chinese — or about a quarter of the country’s population — will be over age 65. And dramatically improved life expectancy and rising incomes have afforded these older people a freedom to enjoy life post-retirement in a way that would have been unthinkable for their parents’ generation. “Retired life is better than we could have ever imagined,” said Sheng Shengmin, 67, a retired building contractor from Beijing. Last year, Mr. Sheng joined the wave of snowbirds who have laid down roots here, buying an apartment in the city for the equivalent of $272,000. After years of living in Beijing, Mr. Sheng said, “the pollution, the migrant workers, and the cold” had made the capital city uninhabitable. “Once you retire and you’ve saved up enough money, you don’t want to go back to living in the big cities,” Mr. Sheng said as he took a sip from his tea thermos, a common accessory for many older Chinese. That so many Chinese retirees would leave behind their homes to live in an unfamiliar city is all the more remarkable given China’s tradition of filial piety. For generations, children in China have grown up with the expectation that they would one day care for their aging parents. But there are growing concerns that responsibility may be too much for the generation of only children produced by the “one-child” policy to handle on their own. As a result, more empty nesters in China are adopting the snowbird lifestyle with the aim of easing the burden on their children. “Right now, it’s fine because we’re healthy,” said Zhao Kaile, 62, a retired railway bureau administrator and a native of Mudanjiang in northeastern China. “But twenty years from now, will we be able to take care of ourselves without our children? Everybody is thinking about this problem now.” As the head of the migrants association in a suburban community all but taken over by snowbirds, Mr. Zhao spends much of his time coordinating meetings and music rehearsals. On a recent morning, more than 60 retirees gathered together in the community recreation room to rehearse sentimental favorites like “Onwards, Chinese Communist Party” and more recent hits like “Together Build the Chinese Dream.” Accompanying the chorus was a boisterous band of graying musicians, including a piccoloist and an electric guitarist. “Before, we thought retired life would be very dull, just sitting on little stools in the sun and shriveling up and growing old,” said Mr. Zhao. “But our lives have transformed. We had no idea that after coming here we would be so happy and have so many friends.” Not everyone is happy with the presence of Sanya’s snowbirds. The annual influx, which began in the early 2000s, has created tensions with local residents, who are increasingly outnumbered by their seasonal visitors. Locals complain that the retirees have driven up the cost of housing and food while simultaneously taking advantage of public services like transportation and hospitals. They find peace only in the off-season summer months, when the snowbirds retreat to their homes up north to escape the sweltering temperatures and monsoon rains. Several years ago, the local government began razing large tracts of housing in the city, in what many see as an ongoing effort to drive out the often frugal snowbirds by denying them places to rent. Others say the goal is instead to attract high-spending vacationers to boost local tourism, already one of the city’s main industries in addition to agriculture. “Sanya wants to be known as an international tourism destination, not as an elderly retirement community,” said Huang Cheng, a lecturer at the University of Sanya who has studied the local snowbird phenomenon. Several months ago, Wen Zhiguo, manager of a local hotel that caters to aging snowbirds, was forced to move to the outskirts of the city after the local government tore down his seaside facilities. Despite the change in location, Mr. Wen continues to run a brisk business renting out rooms to retirees who pay about $350 a month in exchange for simple accommodation and three meals a day. On a recent afternoon, the lobby of Mr. Wen’s hotel began to stir as guests rose from their lunchtime naps. The choice of activities was plentiful — calligraphy, mah-jongg, cards and table tennis — and the faint scent of medicinal ointment infused the sunlit room. A stately looking man with a snow-white coif sat quietly at a table playing a game of mah-jongg solitaire. A retired soldier in the People’s Liberation Army, Wang Xingeng, 89, remembered the first time he visited Sanya more than a half-century ago, just after the Communist Party’s 1949 takeover. “Back then, the island was all shabby little huts, there were no buildings,” Mr. Wang said. “It was the poorest place I’d ever seen. It’s where they sent criminals.” “I never thought I’d be back here,” he added, looking around pensively at his fellow snowbirds. “But now I’ve come full circle.” The New York Times