The Hong Kong Observatory (HKO) raised the storm signal to T10 Sunday morning local time, closing shops and suspending transport as residents were warned to stay inside and well away from the water’s edge.
Mangkhut is already the storm of 2018, and is currently packing sustained winds of 165 kilometers per hour (103 miles per hour), with gusts up to 205 kilometers per hour (127 miles per hour).
Earlier on Saturday, it plowed into the Philippines, killing at least two people and flattening homes in small towns and villages on the northern island of Luzon.
Mangkhut is now some 220 kilometers (136 miles) south-southeast of the city, and heading for the surrounding Pearl River Delta, home to 120 million people.
The storm is expected to be one for Hong Kong’s record books. It’s only the 15th time in the last 60 years that a T10 has been hoisted; the last was for Super Typhoon Hato last year.
The city’s famed Victoria Harbor is expected to see a storm surge of 3.5 meters later Sunday (11.5 feet).
Hundreds of flights from the city’s airports were delayed or canceled, and much of the city’s public transport has been suspended.
Hong Kong authorities have been warning residents about the storm for days, and come Saturday, grocery stores were packed with people stocking up on goods. Buildings across the city were either boarded up or had their windows taped in order to mitigate the damage of broken glass.
The storm is currently moving 30 kilometers per hour (19 miles per hour) toward the coast of western Guangdong, mainland China, according to the HKO.
It’s expected to pass about 100 kilometers (62 miles) south of the Pearl River Delta — an area in southern China that includes the cities of Hong Kong, Guangzhou, Shenzhen, Zhuhai and Macau — at about noon Hong Kong time Sunday, according to the the HKO.
However, the storm has weakened and is now classified by the HKO as a severe typhoon rather than a super typhoon. But officials in Hong Kong are still warning residents to be cautious.
“Although Mangkhut has weakened slightly, its circulation is extensive and winds remain fierce,” the HKO said. “Members of the public should stay on high alert, and note the impacts of changes in wind direction.”
Mangkhut slams into the Philippines
Mangkhut struck the northern Philippines as a super typhoon, killing at last two people and causing flooding and landslides on the northern island of Luzon.
It made landfall in the Philippines Saturday at 1:40 a.m. local time, packing winds of up to 270 kph (165 mph), 120 kph (75 mph) stronger than Hurricane Florence that hit North Carolina.
Known locally as Ompong, Mangkhut ripped roofs off buildings, uprooted trees, blocked roads with debris and dumped water on fields of crops.
The most severe damage came in Luzon’s north, a sparsely populated region that’s considered the breadbasket of the Philippines, though areas as far away as Manila — more than 340 km (200 miles) from the eye of the storm — were hit with heavy rains that caused flooding in urban areas.
Though the storm system has moved on, extent of the damage has been difficult to asses Sunday as fierce winds were replaced by flood waters, blocking access and aid to affected areas.
Mangkhut is expected to make another landfall late Sunday night, hitting the Chinese province of Guandong near the cities of Yangjiang and Zhanjiang.
From there the system will continue to move westward and will rain itself out over northern Vietnam, which could lead to some flooding there early next week.
CNN’s Jo Shelly and Alexandra Field in Santiago, Philippines, contributed to this report