Typhoon Usagi has killed at least 25 people in Guangdong province of south China, the government has said.
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.
However, 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, the state-run Xinhua news agency reported. Power supplies in many parts of the province and in Guangdong have been cut off.
The typhoon caused 7,100 homes to collapse and led to direct economic losses of 3.24 bn yuan ($526m; £329m), Xinhua added.
"It is the strongest typhoon I have ever encountered," Xinhua 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."
Hong Kong's port - one of the world's busiest - shut down as the densely populated territory braced itself for the storm - the most powerful of this year.
Although officials say that Hong Kong escaped the worst ravages of the weather, the South China Morning Post said that Usagi still caused disruption and disarray, bringing flooding to some areas.
More than 400 flights were cancelled or delayed, Hong Kong's Airport Authority said.
Just after 18:00 BST on Sunday the Post reported that Usagi's designation had been reduced from Severe Typhoon to Typhoon and it was moving away from Hong Kong.
On Monday, classes were suspended in Hong Kong, Macau and 14 cities in Guangdong province, Xinhua reported.
Usagi - which means rabbit in Japanese - had produced winds of 165 km/h (103 mph) as it closed in on China's densely populated Pearl River Delta.
China's National Meteorological Centre warned that Usagi would bring gales and downpours to parts of the southern coast.
People living in southern China are used to typhoons, but Usagi hit the region with unusual force, the BBC's Celia Hatton in Beijing reports.
The storm hit just as millions were travelling for China's mid-Autumn festival - a national, three day holiday when many visit family - leading to flight and high speed train cancellations, our correspondent adds.
The storm crossed through the Luzon Strait between Taiwan and the Philippines on Friday.
Parts of the Philippines were badly hit by floods caused by the typhoon on Monday.
Officials said at least 18 people were killed in floods and landslides in the north western Philippines.
The province of Zambales was particularly badly affected, assistant civil defence director Nigel Lontoc told AFP news agency.
"This is mountainous area and there are many houses on the slopes. The rain must have really weakened the soil," he said.
Kay Khonghun, mayor of Subic, northwest of Philippine capital Manila, told AFP his town had been hit by flood water that was "chest-deep in many areas".
"The rain is pounding and the water keeps on rising," he said.
Typhoons are common during the summer in parts of East Asia, where the warm moist air and low pressure conditions enable tropical cyclones to form.