NEW YORK (NYTIMES) Just three days ago, the River Des Peres, which carries stormwater from the city of St. Louis, was "almost bone dry," the city's fire chief said, as Missouri experienced what the governor called increasingly dry conditions and the growing threat of serious drought.

Then came record rainfall early Tuesday, drenching parts of St. Louis and other areas of Missouri with up to 30cm of rain that quickly transformed interstates and neighbourhood streets into roaring rivers that collapsed roofs and forced residents to flee their homes in inflatable boats.

While officials worked to assess the full scope of the damage, Chief Dennis Jenkerson of the St. Louis Fire Department said at a news conference on Tuesday (July 26) that one person who had been pulled from a flooded vehicle had died. There was about 2.5m of water in the area, he said.

Firefighters had helped or rescued about 70 residents, he said.

Property damage was "very significant" in some hard-hit areas, he said, including one in the southwestern part of the city where 14 or 15 homes had experienced "significant floodin".

"We've had a tremendous amount of cars that have been door-deep and also roof-deep in some of these low-lying areas," Mr Jenkerson said.

"Now, we're seeing the weight of the water cause some issues with buildings. We're having some partial roof collapses. Some of the vacant buildings are also suffering from the stress of this water."

The flash flooding was only the latest entry in what seemed to be an unceasing onslaught of extreme weather disasters, with ferocious wildfires, punishing heat waves, crippling droughts and deadly floods in the United States and across the globe.

While a variety of factors contribute to flooding, researchers expect that, as the climate warms, flash floods will increase and get "flashier", meaning their duration will shorten as their magnitude increases. Severe flash floods can be more dangerous and destructive.

Tuesday's flood showed that St. Louis' storm systems were already "under exorbitant stress" from development, said Mr Derek Hoeferlin, an associate professor and chair of the landscape architecture and urban design programs at Washington University in St. Louis.

Governor Mike Parson of Missouri, who was on a trade mission in Germany, said he had been monitoring the rainfall from afar.

He and the lieutenant governor declared a state of emergency on Tuesday, allowing the state to coordinate directly with local officials and provide assistance.

The St. Louis area also flooded nearly three decades ago, when the Mississippi and Missouri rivers swamped villages and farmland during a two-month inundation that came to be known as the great Midwest flood of 1993.

That flood claimed 50 lives across the region, left almost 70,000 people homeless and caused an estimated US$12 billion (S$17 billion) in property and agricultural damage.

City officials said they were not sure how many people had been displaced in Tuesday's storm, but Mr Jim Sieveking, a meteorologist with the National Weather Service in St. Louis, described the flash flooding as "catastrophic" and the rainfall as "historic".

More than 22cm of rain fell in the St. Louis area overnight, the highest 24-hour rainfall total on record there, the weather service said.

It surpassed the18cm that fell in 1915 from the remnants of the Galveston hurricane. The normal amount of rain in St. Louis for July and August combined is 18cm.

By Tuesday morning, 25cm to 30cm of rain had fallen in parts of eastern Missouri, the weather service said. The largest total was 31cm in St. Peters, northwest of St. Louis, the agency said, noting that rain continued to fall.

The flooding shut down more than two dozen sections of major roads that crisscross the St. Louis area, including Interstate 170, a beltway that runs north and south, and Interstate 70, which runs east and west, the state Department of Transportation said.

Mr Steve Gibson, 60, an aircraft mechanic who lives in southwest St. Louis, said a neighbour had called him at 3.30am, telling him that his car was floating down the street.

Gibson went next door to check on his 88-year-old father, Bob, who has a pacemaker and mobility issues, and found him sitting at the kitchen table with his feet underwater.

Mr Gibson said he helped move his father to a garage. As they were walking there, with water reaching his chest, Mr Gibson said he suddenly felt an electrical shock.

Firefighters, who had blocked off the road, rescued Mr Bob Gibson by boat. But Mr Steve Gibson's wife, Gina, an emergency nurse, had to postpone the start of radiation treatment Tuesday for metastatic cancer, which had reached her lungs, breast and brain, she said.

"She's my No. 1 priority," Mr Gibson said of his wife.

The Gibsons, like many in the neighbourhood, said they had never experienced such flooding. The threat had appeared so small that they had cancelled their flood insurance about 18 months ago.

"We have been here for 25 years, and we have never even had water" damage, Mr Gibson said.

But now, he added, "so much of our stuff is ruined".