Extreme weather events have become more frequent and severe in China, testing the top-down and increasingly centralized leadership under Xi Jinping that can weaken local governments' responses to such disasters.
The floods also threaten the country's uneven economic recovery by hitting one of its most populous and wealthy regions. Guangdong, a key manufacturing and trade hub, is home to more than 127 million people and is China's economic powerhouse.
The region has been hit by heavy rains since Thursday, causing landslides that buried buildings and floods covering villages and towns. Provincial authorities issued 148 storm warnings on Sunday and said the Bay River was expected to reach levels not seen in 50 years.
Footage broadcast by Chinese media showed rescue crews pulling residents from cars and houses and ferrying them across submerged streets.
More than 82,000 people have been evacuated from their homes, authorities said. At least 1.16 million households lost power due to the storms and more than 1,000 schools were closed on Monday. At least four weather stations in the region reported record rainfall for the month of April on Sunday.
Communications links to the Jiangwan municipality in Guangdong, home to about 3,600 people, were cut due to flooding on Sunday and were only partially restored on Monday using satellite links and drones, according to state media. A team of 80 rescuers trekked through the night to reach the area on Monday, where several buildings were covered by landslides.
A cross-country race had to be abandoned on Sunday after runners were temporarily trapped in the forest with floodwaters up to their waists before being rescued.
