Typhoon Mangkhut is lashing China's most populous province, bringing winds of up to 100 mph (162 kph).
Guangdong is on its highest alert for the storm, which also hit Hong Kong, where it swayed skyscrapers and blew out windows.
The death toll from the Philippines has now risen to at least 59. Most died in landslides caused by heavy rain.
Mangkhut, considered the strongest storm of 2018, ploughed through the northern Philippines on Saturday.
More than 2.45 million people have been relocated, and authorities there issued their highest warning level, a red alert.
In Hong Kong, authorities also issued their maximum alert, with residents warned to stay indoors to avoid flying debris. Winds there reportedly reached more than 110 mph (177 kph).
Officials put the number of injured at more than 200 but the territory avoided the worst of the storm.
Water levels surged by almost 3.5 m (12 ft) in places and live fish were washed on to the streets.
Most shops and public services were shut, and more than 800 flights have been cancelled at Hong Kong International Airport - affecting more than 100,000 passengers.
In neighbouring Macau, for the first time in its history the territory's famous casinos were ordered to close.
Mangkhut is expected to weaken into a tropical depression by Tuesday as it moves inland.