Southern Chinese authorities have called for a "wartime" footing in anticipation of one of the world's strongest storms this year, with preparations under way on Tuesday to close roads and rail lines, cancel school classes and evacuate hundreds of thousands of people.
Super Typhoon Ragasa is forecast to pass through China's Pearl River Estuary, the delta that is home to some of the country's biggest technology and manufacturing hubs, on Wednesday morning.
Weather conditions in the region are expected to deteriorate "rapidly" from Tuesday afternoon, according to the Hong Kong Observatory.
A super typhoon is the strongest category of tropical cyclone, with sustained winds of more than 185km an hour. Winds at Ragasa's centre were as high as 230km an hour early Tuesday. They have since moderated to about 220km an hour, the equivalent of a category 4 hurricane, according to HKO.
The storm passed over the Philippines on Monday, and has prompted warnings from as far away as Taiwan.
The typhoon will be the ninth to trigger a storm warning in Hong Kong and southern China this year. Historically, Hong Kong has recorded an average of six such storms a season, which typically lasts until about mid-November, according to research by the City University of Hong Kong.
The Chinese Communist party secretary for southern Guangdong province, which borders Hong Kong, told a meeting on Monday to prepare for "an emergency footing and a wartime state", according to state media.
"We must resolutely win the hard-fought battle of preparing for this typhoon and exert ourselves in reducing the harm caused to a minimum," said Huang Kunming.
In Dongguan, an electronics manufacturing hub between the provincial capital Guangzhou and tech megacity Shenzhen, authorities began enforcing what they called "five cancellations" -- schools, production, work, operations and businesses -- in phases from Monday afternoon.
Similar measures were under way in Shenzhen, Zhuhai and Foshan, as well as districts of a number of other cities. In Shenzhen, authorities said they had opened 865 emergency shelters and that 400,000 people would need to be evacuated.
Transport was also disrupted across the region. Hong Kong's flagship carrier Cathay Pacific saying it expected to cancel more than 500 flights between Tuesday and Thursday, although the territory's airport authority said it would remain open during the storm.
School classes in Hong Kong were also suspended for Tuesday and Wednesday, as officials warn that winds may reach "hurricane force".
In Dongguan, all roads will be closed to non-emergency vehicles from 2pm on Tuesday. State media reported that provincial authorities ordered both high-speed and regular trains to begin phased cancellations from Tuesday afternoon, with all rail services suspended by Wednesday.
Officials have directed supermarket chains, including Walmart, and food delivery platform Meituan to increase supplies of essential goods and refrain from price gouging, according to statements issued by local governments.
Trading on Hong Kong's stock exchange is set to continue during the storm, under a mechanism introduced last year allowing it to maintain operations under adverse weather events.
Flooding is expected in many areas. Officials said sea levels in coastal areas could reach levels comparable to Typhoon Hato in 2017 and Typhoon Mangkhut in 2018, which inflicted an estimated hundreds of millions of dollars in economic losses to the territory.