Mangkhut weakened from a typhoon to a tropical storm as it moved deeper into southern China yesterday, but leaving death and destruction in its wake, from Hong Kong to the Philippines.
The storm was still affecting southern China's coast and the provinces of Guangdong, Guangxi and Hainan, and rain and strong winds were expected to continue through today.
Hong Kong residents were told to stay away from the coastline and be on alert for occasional gales.
Bus, ferry and rail services were suspended and almost 900 flights were cancelled at the city's airport, one of the world's busiest.
The South China Morning Post said Hong Kong's hospitals had to use back-up power due to outages caused by the storm.
Philippine and Chinese authorities said the death toll from the typhoon has risen to at least 69, with dozens more people missing.
The Hong Kong Observatory reported Mangkhut was the most powerful cyclone to hit the city since 1979, packing maximum sustained gusts of 121mph.
"Prepare for the worst," Hong Kong Security Minister John Lee Ka-chiu urged residents.
More than 2.4m people had been evacuated in southern China's Guangdong province by Sunday evening. Meanwhile, in the United States, access has been restored into the city of Wilmington, which had previously been cut off by floods from former Hurricane Florence.
Department of Transportation secretary James Trogdon said there is one major accessible route into the city of nearly 120,000 people.
Emergency workers were delivering truckloads of food and water to Wilmington as helicopters and boats pulled people from homes swamped by swollen rivers.
Flooding worries increased in West Virginia and Virginia, where roads were closed and power outages were on the rise. About 500,000 homes and businesses were in the dark.
The death toll climbed to 20 as authorities found the body of a one-year-old boy who was swept away after his mother drove into floodwaters and lost her grip on him while trying to get back to dry land, and an 88-year-old man's car was swept off a road.
Florence was still massive, despite being downgraded to a tropical depression from a once-fearsome Category 4 hurricane.
Radar images showed parts of the sprawling storm over six states, with North and South Carolina in the eye of the tempest.