Typhoon Usagi has killed at least 25 people in Guangdong province of south China, the government said on Monday.
Winds of up to 180 km/h (110 mph) were recorded in some areas, toppling trees and blowing cars off roads. Its victims drowned or were hit by debris.
The storm has affected 3.5 million people on the Chinese mainland. Trains from Guangzhou to Beijing have been suspended and hundreds of flights from Guangzhou, Shenzhen and Hong Kong have been cancelled.
Hong Kong has escaped the worst of the storm.
Weather officials say that the ferocity of the storm has abated as it progressed into southern China, but financial markets in Hong Kong were closed for part of Monday morning.
More than 80,000 people were moved to safety in Fujian province and the authorities have deployed at least 50,000 relief workers, a state-run international news agency reported. Power supplies in many parts of the province and in Guangdong have been cut off.
“It is the strongest typhoon I have ever encountered,” the international news agency quoted Luo Hailing, a petrol station attendant in Shanwei – in the eastern part of Guangdong province – as saying. “[It was] so terrible, lucky we made preparations.”