Some areas on the northwest side of St. Louis received more than 10 inches of rain in six hours overnight — an event with a 0.1 percent chance of happening in a given year. The heaviest rain had moved off to the northeast by 8 a.m., but downpours continued to affect the city.
Emergency workers were responding to numerous reports of drivers whose cars were submerged in the flooding. On one block in the western part of the city, the St. Louis Fire Department said, it had used an inflatable boat to rescue six people and six dogs trapped in about 18 homes amid severe flooding. About 15 people chose to shelter in place.
No injuries from the flooding had been reported as of about 10 a.m. local time, said Ann Vastmans, a spokeswoman for the St. Louis County Office of Emergency Management.
Videos shared on social media showed many roads completely inaccessible. Part of a major highway, Interstate 70, was closed because of the flooding, the Missouri Department of Transportation said.
St. Louis County emergency officials urged residents not to travel and said they had set up a shelter for displaced people. The central part of the county was most affected by the downpour, they said.
“Exercise extreme caution,” St. Louis firefighter Garon Patrick Mosby said in a video shared on Twitter. “We are being overrun here.”
Extreme precipitation events have increased substantially over the past century and are tied to warming from human-caused climate change. The heaviest such events increased by 42 percent in the Midwest between 1901 and 2016, with additional increases expected as the climate continues to warm, according to the U.S. government’s National Climate Assessment.
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The rain in St. Louis began late Monday as thunderstorms formed along a west-to-east line, repeatedly passing over the city like train cars on a track into Tuesday morning. The National Weather Service warned of “life threatening flash flooding” just after 2 a.m. and later declared a flash flood emergency, its most serious flood alert. By then, 3 to 6 inches of rain had fallen and high water was “threatening houses” while vehicles were submerged in high water, according to the Weather Service.
“This is a PARTICULARLY DANGEROUS SITUATION,” it warned. “SEEK HIGHER GROUND NOW!”
St. Louis received the equivalent of two months’ worth of rain in six hours. A creek in St. Peters, Mo., just northwest of St. Louis, rose 21.5 feet in seven hours to a record crest amid the torrent.
The thunderstorms formed along the northern periphery of a heat dome sprawled over the south-central states, responsible in recent days for record-high temperatures in parts of Texas, Oklahoma and Arkansas. St. Louis was situated in the turbulent transition zone between that oppressive heat and cooler weather entering the Upper Midwest from Canada.
On Tuesday, the Weather Service declared the area from eastern Missouri to central West Virginia under an elevated risk for excessive rainfall, with the greatest risk from the St. Louis area through southern Illinois and into southwest Indiana. That risk is forecast to shift into the area from southeast Missouri through West Virginia on Wednesday and Thursday.