Beijing residents expressed fury on Monday after the worst rains to hit the Chinese capital in more than 60 years left at least 37 people dead, with at least another seven still missing.

Many said lives could have been saved and some of the worst devastation avoided if a better warning system had been in place, and criticised the city's antiquated water infrastructure.

"If the drainage system had been good, if the warning system had been put in place in a timely manner, if people had been told to stay home, would so many people have lost their cherished lives?" read one posting, under the name Bijiexiang.

By Monday morning, there were nearly nine million comments on the Sina Weibo microblog alone.

In the worst-hit district of Fangshan, on the mountainous southwestern outskirts of China's sprawling capital, residents described how roads flooded in minutes, submerging vehicles and destroying houses.

Fangshan farmer Wang Ping, 56, was still looking for his 30-year-old son on a lake shore after finding his smashed up car, and complained that the government was doing nothing to help.

"My son called around nine o'clock on Saturday evening and he said he was surrounded by water, so I went to search for him," Wang told AFP, in between shouting out his name.

"The government isn't doing anything to help me find my son."

In the nearby tourist village of Shidu, villagers were left to clear up the damage to their restaurants, guesthouses and shops after they were battered by trees swept down the overflowing Juma river.

"We never bought insurance, never expected a flood this big," Yang Xing, an 18-year-old student, told AFP as he cleared up broken glass at his grandparents' restaurant.

At least 25 people drowned in Saturday's rains, the heaviest in the capital since records began in 1951. Six died in housing collapses, five were electrocuted and one person was struck by lighting.

The same storm left another 17 people dead and 21 missing in the neighbouring province of Hebei, the China News Service said.

The rains and flooding caused 10 billion yuan-worth ($1.6 billion) of damage in Beijing, while nearly 66,000 people had to be evacuated from their homes, state media said, citing the city government.

"Chinese cities are apparently unpractised in facing disasters such as Saturday's torrential downpour," the Global Times daily said in a Monday editorial critical of the authorities' disaster preparedness.

"If so much chaos can be triggered in Beijing, the capital of the nation, problems in urban infrastructure of many other places can only be worse."

Pictures showed entire parking lots flooded, while rescue and traffic workers were seen diving underwater to unclog roadside drains as helpless drivers looked on from partially submerged cars.

Many roads in the capital were inundated by up to a metre (three feet) of water, while 500 outbound flights were cancelled and at least 80,000 passengers stranded.

Parts of the Beijing-Guangdong highway, a major arterial route to the south, remained flooded on Monday, the Beijing traffic bureau said.

Much of Beijing's central drainage system dates from imperial times, including the moat around the Forbidden City.

The rain lasted for about 16 hours on Saturday and up to 46 centimetres (around 18 inches) fell on the outlying mountainous district of Fangshan, the Xinhua news agency said.

Some state-run media focused on how the rains brought the city of more than 20 million people together, with police and traffic workers joining hands with ordinary citizens to rescue stranded motorists.

Xinhua reported that the rains had filled Beijing's 17 major reservoirs, many of which had lacked water due to a 13-year drought.

China's finance ministry has allocated 120 million yuan in relief funds to help Beijing, neighbouring Tianjin city and Hebei province handle the disaster.

Xinhua also said eight people were confirmed dead due to heavy downpours in Sichuan province, in the nation's southwest.

China is routinely ravaged by summertime flooding, which normally wreaks havoc in regions along the central Yangtze river and in the south, but floods are relatively rare in Beijing, which usually has a dry climate.