In under a day, parts of central North Carolina were inundated with record-breaking rain. Nearly 9 inches fell in Chapel Hill, and some areas of Chatham County saw close to 1 foot of water. Streets turned to rivers, cars were submerged and emergency crews rescued more than 200 people from rising floodwaters.
Officials declared a state of emergency Sunday night. By Monday morning, the images had already gone viral: a Trader Joe’s parking lot turned into a brownwater basin, a road split open in Durham, and cars disappearing under water.
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The storm, once Tropical Storm Chantal, had weakened into a tropical depression by the time it reached central North Carolina. But the damage left behind was anything but weak.
According to hydrologists, the rainfall met the threshold for a 1,000-year flood. That classification refers to a statistical probability, meaning there is just a 0.1 percent chance of that much rain falling in a given year, but it does not mean the region won’t see something similar again soon.
“It’s definitely jarring to see it happen in North Carolina, especially so close to home,” said Helena Garcia, a Ph.D. candidate at UNC Chapel Hill who studies flood impacts across the state. “Flooding isn’t just a coastal issue. We're seeing more of this frequent flooding inland."
North Carolina is no stranger to extreme rainfall. Hurricanes like Fran, Floyd, and Florence each brought widespread flooding and loss of life to the state. But Sunday’s rainfall total in Chapel Hill exceeded all three of those historic storms in some locations, according to preliminary National Weather Service data.
The difference this time is not just the amount of rain, but the rate at which it fell. Data from the National Oceanic and Atmospheric Administration, analyzed by Climate Central, shows that rainfall intensity in the Raleigh-Durham area has increased 21% since 1970.
“We’re seeing a trend where more rain is falling in less time,” said Shel Winkley, a meteorologist with Climate Central. “That’s a problem for drainage systems, for infrastructure, for flash flood risk and it’s exactly what we expect in a warming world.”
Winkley said climate change is playing a measurable role in making heavy rainfall events more dangerous. As greenhouse gases trap more heat in the atmosphere, the air holds more moisture. For every degree Fahrenheit of warming, the atmosphere can absorb roughly 4% more water vapor. That extra moisture is then released more rapidly during storms, increasing the intensity of rainfall.
“It’s not that storms like this wouldn’t happen without climate change,” Winkley said. “But what we’re seeing is that climate change is supercharging them. It adds more fuel to the system, turning a heavy rain event into a flooding disaster.”
According to a national analysis from Climate Central, rainfall intensity has increased in 88% of the 144 U.S. cities studied since 1970.
Inland flooding is also becoming more common. A recent Climate Central study estimated that more than one-third of the $230 billion in inland flood damage in the United States between 1988 and 2021 would not have occurred without human-caused climate change.
Garcia, whose research focuses on flood impacts across North Carolina, said the flooding in Chapel Hill highlights a deeper issue: many residents may not know they are at risk.
In a recent analysis of past flood events in the state, Garcia and her team found that a large portion of flooded properties were located outside of FEMA-designated flood zones.
“That’s a huge problem,” Garcia said. “The FEMA 100-year floodplain is the only publicly available tool people really have to gauge their risk. But it’s outdated and incomplete. We’ve seen time and time again that people can flood well outside of those mapped areas.”
The consequences of that underestimation can be costly. Many homeowners outside the FEMA zones may not be required to carry flood insurance, and they may be less prepared for fast-moving water.
“Flash flooding doesn’t give you much time to react,” Garcia said. “It’s critical that people have better information, better communication from local officials, and better preparedness systems in place.”
She also pointed to the limitations of stormwater infrastructure in growing cities like Chapel Hill and Durham. Rapid development in flood-prone areas, she said, has made the region more vulnerable to flooding. And the solutions are not simple.
“A lot of this development is already built,” Garcia said. “We can’t undo that. But we can reduce risk by improving drainage systems, elevating homes where possible, and making sure residents and business owners know how to respond before the next storm.”
Winkley said attribution studies are still being conducted to quantify climate change’s specific influence on this storm, but there are attribution studies for the broader pattern.
“We are taking natural weather systems and adding an unnatural layer,” Winkley said. “It’s like turning up the volume. The storms don’t just pass through, they roar through, and they leave real damage behind.”
With hurricane season underway and Atlantic Ocean temperatures running above average, scientists warn that more flood events may be on the horizon.
“We’re only in July,” Winkley said. “There’s a long way to go this season."