Hurricane Sally yesterday moved north-east, where it was expected to bring more than 30cm of rain to some areas a day after it flooded streets and knocked out power to hundreds of thousands of homes on the US Gulf Coast.
Sally made landfall early on Wednesday near Gulf Shores, Alabama, as a Category 2 storm on the five-step Saffir-Simpson scale of intensity.
As of late Wednesday, it was moving north at 15kmh after being downgraded to a tropical depression, the United States National Hurricane Centre said, with maximum winds of 55kmh.
The storm is believed to have killed one person in Alabama.
Some parts of the coast were inundated with more than 60cm of rain, as the storm flooded communities.
The coastal community of Pensacola, Florida, experienced up to 1.5m of flooding and travel was cut by damaged roads and bridges.
More than 570,000 homes and businesses across the area were without power.
Several residents along the Alabama and Florida coasts said that damage from the slow-moving storm caught them off guard.
"It was recently constant rain and wind," said Ms Preity Patel, 41, a resident of Pensacola for two years.
"The water drained pretty quickly, thankfully. It's just clean-up now."
A section of the Pensacola Bay Bridge, known also as the Three-Mile Bridge, was missing a "significant section", Florida Governor Ron DeSantis said.
On landfall in Gulf Shores Sally's winds were clocked at 169kmh. Along the coast, piers were ripped away by the storm surge and winds.
"This year, we've just got hurricane after hurricane," said Mr Matt Lane, 23, a member of an electrical crew from New Hampshire Electric Co-op, who arrived in Pensacola late on Tuesday directly from Hurricane Laura recovery efforts in Texas.
Sally was the 18th named storm in the Atlantic this year and the eighth of tropical storm or hurricane strength to hit the US.
There are currently three other named storms in the Atlantic, making it one of the most active Atlantic hurricane seasons on record.
As hurricanes go, Sally was not especially powerful. But climate change likely made it more dangerous by slowing it down and feeding it more moisture, setting it up to pummel the region with wind and catastrophic rainfall.
"When a storm moves slower, it lingers longer over the same location," said Assistant Professor Kimberly Wood, a geoscientist at Mississippi State University.
"A rain rate of, say, 2.5cm an hourthat's not so bad if the rain only lasts 30 minutes. But if it lasts for half a day, that adds up quickly."
And there is increasing evidence that storms are slowing down, Prof Wood said.
That evidence comes in part from a 2018 study that showed hurricanes near the Gulf and Atlantic coasts were increasingly likely to stall.
The study also found a clear signal of more local rainfall, said Dr James Kossin, a researcher with the National Oceanic and Atmospheric Administration (NOAA), who is one of the authors.
Prof Wood said that climate change has led to wetter storms because warmer air holds more moisture.
Between the slowing speeds and increasing moisture, with storms like Sally, "there's a combination effect", she said.
Dr Sarah Kapnick, a researcher at NOAA's Geophysical Fluid Dynamics Laboratory in Princeton, New Jersey, said: "There's a basic theoretical understanding underlying all of this.
"(With warming,) you get more water vapour in the sky. So when you get these storms... they have the potential to hold more water in them."
She added: "And that water has to go somewhere."
REUTERS, NYTIMES