At least 20 people are dead and 19 missing after heavy rains lashed Beijing, Chinese state broadcaster CCTV has said.
A military unit of 26 soldiers and four helicopters launched an "airdrop rescue mission" in the early hours of Tuesday to deliver hundreds of food packages and ponchos to people stranded in and around a train station in Beijing's hard-hit Mentougou district, state broadcaster CCTV reported.
"On July 31, areas in Beijing including Fangshan and Mentougou suffered serious damage from water, causing three trains to get trapped on their routes and road traffic in some areas was completely cut off," CCTV reported.
Around 150,000 households in Mentougou had no running water, the local Communist Party newspaper Beijing Daily said, with 45 water tankers dispatched to offer emergency supplies.
Chinese President Xi Jinping called for "every effort" to rescue those "lost or trapped".
"Xi Jinping demanded that all localities should make every effort to search for and rescue lost and trapped persons," state broadcaster CCTV reported, adding they "must do a good job in treating the injured and comforting the families of victims, and minimise casualties."
Local media on Monday published footage of chaotic scenes aboard high-speed rail trains stranded on tracks for as long as 30 hours, with passengers complaining that they had run out of food and water.
Storm Doksuri, a former super typhoon, has swept northwards over China since Friday, when it hit southern Fujian province after scything through the Philippines.
Heavy rains began pummelling the capital and surrounding areas on Saturday, with nearly the average rainfall for the entire month of July dumped on Beijing in just 40 hours.
Beijing and neighbouring Hebei province were on red alert overnight for rainstorms, with meteorological authorities warning of potential flash floods and landslides.
The city activated a flood control reservoir on Monday for the first time since it was built in 1998, the Beijing Daily said.
In Handan, Hebei province, rescuers lifted by crane reached a man trapped on his car in floodwaters on Sunday, lifting him to safety before the car was flipped and washed away by the current.
Experts had warned that the downpour could prompt even worse flooding than in July 2012, when 79 people were killed and tens of thousands evacuated, according to local media.
The country is already preparing for the arrival of another typhoon — Khanun, the sixth such storm of the year — as it nears China's east coast.