People shop at a duty free shop in Haikou, capital of south China's Hainan Province, May 2, 2019. (Xinhua/Guo Cheng)

People buy goods at a duty free shop at Sun Moon Plaza in Haikou, capital of south China's Hainan Province, May 2, 2019. (Xinhua/Guo Cheng)

People shop at a duty free shop in Haikou, capital of south China's Hainan Province, May 2, 2019. (Xinhua/Guo Cheng)

Tourists watch a dolphin show at Xin'ao Aquarium in Qinhuangdao, north China's Hebei Province, May 2, 2019. (Xinhua/Cao Jianxiong)

Tourists take part in a bamboo dance at Nanshan Cultural Tourism Zone in Sanya, south China's Hainan Province, May 2, 2019. (Xinhua/Chen Wenwu)

People visit the Luyang Lake wetland park in Yangzhou, east China's Jiangsu Province, May 2, 2019. (Xinhua/Meng Delong)

Tourists have fun at Xin'ao Aquarium in Qinhuangdao, north China's Hebei Province, May 2, 2019. (Xinhua/Cao Jianxiong)

Tourists visit the Yuhuagu scenic area in Qianxi County in Tangshan, north China's Hebei Province, May 2, 2019. (Xinhua/Wang Aijun)

Tourists take boats at Jinshan Lake scenic spot in Zhenjiang, east China's Jiangsu Province, May 2, 2019. (Xinhua/Chen Gang)

Aerial photo taken on May 2, 2019 shows tourists visiting the Luyang Lake wetland park in Yangzhou, east China's Jiangsu Province. (Xinhua/Meng Delong)

Tourists walk on a glass bridge at a scenic spot in Zigui County, Yichang, central China's Hubei Province, May 2, 2019. (Xinhua/Wang Gang)

Tourists ride camels at the Mingsha Mountain and Crescent Spring scenic area in Dunhuang, northwest China's Gansu Province, May 2, 2019. (Xinhua/Zhang Xiaoliang)

Tourists visit the Mingsha Mountain and Crescent Spring scenic area in Dunhuang, northwest China's Gansu Province, May 2, 2019. (Xinhua/Zhang Xiaoliang)

A tourist ziplines at a scenic spot in Zigui County, Yichang, central China's Hubei Province, May 2, 2019. (Xinhua/Wang Gang)

Tourists take sightseeing boats at the Fuzi (Confucius) Temple scenic area in Nanjing, capital of east China's Jiangsu Province, May 2, 2019. (Xinhua/Su Yang)

Tourists walk on a glass bridge at a scenic spot in Zigui County, Yichang, central China's Hubei Province, May 2, 2019. (Xinhua/Wang Gang)

Aerial photo taken on May 2, 2019 shows tourists visiting the Zhuoshui ancient town in Qianjiang District, southwest China's Chongqing. (Xinhua/Yang Min)

Aerial photo taken on May 2, 2019 shows tourists visiting Yuhuagu scenic area in Qianxi County in Tangshan, north China's Hebei Province, May 2, 2019. (Xinhua/Wang Aijun)

Performers are seen in an agricultural garden in Laoting County of Tangshan, north China's Hebei Province, May 2, 2019. (Xinhua/Liu Jiangtao)

Tourists visit the Nanshan Cultural Tourism Zone in Sanya, south China's Hainan Province, May 2, 2019. (Xinhua/Chen Wenwu)

Tourists view scenery on bamboo rafts on Jiuqu River of Wuyi Mountain in southeast China's Fujian Province, May 2, 2019. (Xinhua/Qiu Ruquan)

Tourists are seen at the Fuzi (Confucius) Temple scenic area in Nanjing, capital of east China's Jiangsu Province, May 2, 2019. (Xinhua/Su Yang)

Tourists are seen by Songhua River near the square of memorial tower for flood control in Harbin, capital of northeast China's Heilongjiang Province, May 2, 2019. (Xinhua/Wang Jianwei)

Tourists are seen on the Central Street of Harbin, capital of northeast China's Heilongjiang Province, May 2, 2019. (Xinhua/Wang Jianwei)

Tourists are seen at the square of memorial tower for flood control in Harbin, capital of northeast China's Heilongjiang Province, May 2, 2019. (Xinhua/Wang Jianwei)

Children play in Xijingyu Village of Yuyang Township in Jizhou District, north China's Tianjin, May 2, 2019. (Xinhua/Ma Ping)