Liu Nan, a staff member of Tianjin Port, works at Tianjin Port Alliance International Container Terminal in north China's Tianjin, Jan. 6, 2021. Many workers stick to their posts outdoors as the city experiences a strong cold wave that started on Wednesday. (Photo by Zhao Zishuo/Xinhua)

A deliveryman works at Hedong District in north China's Tianjin, Jan. 6, 2021. Many workers stick to their posts outdoors as the city experiences a strong cold wave that started on Wednesday. (Photo by Sun Fanyue/Xinhua)

A deliveryman works at Nankai District in north China's Tianjin, Jan. 6, 2021. Many workers stick to their posts outdoors as the city experiences a strong cold wave that started on Wednesday. (Photo by Li Ran/Xinhua)

Workers work at a construction site of Tianjin Subway Line 11 in north China's Tianjin, Jan. 6, 2021. Many workers stick to their posts outdoors as the city experiences a strong cold wave that started on Wednesday. (Photo by Li Ran/Xinhua)

A sanitation worker adjusts his hat at Nankai District in north China's Tianjin, Jan. 6, 2021. Many workers stick to their posts outdoors as the city experiences a strong cold wave that started on Wednesday. (Photo by Sun Fanyue/Xinhua)

A police officer guides traffic at Heping District in north China's Tianjin, Jan. 6, 2021. Many workers stick to their posts outdoors as the city experiences a strong cold wave that started on Wednesday. (Photo by Sun Fanyue/Xinhua)