An Alarming New Trend in Hurricane Deaths

A week after Hurricane Helene ripped through the American Southeast, it has careened into a terrible category of natural disasters: By some measures, it is now the third-deadliest storm to make landfall in the United States, after Hurricane Maria and Hurricane Katrina. More than 200 people have now been reported dead. Over half of the fatalities so far occurred in North Carolina’s mountainous western region, where entire towns were crushed beneath the weight of relentless rains and crumbling earth. And the death toll is expected to keep rising.

Hurricanes can be extraordinarily lethal. Winds can send trees lurching into living rooms and debris hurtling through the air. Fallen power lines can cause electrocutions. Historically, storm surge—the treacherous rise of seawater as hurricane winds push waves toward shore—has been the deadliest hurricane hazard. But Helene, which did most of its killing far from the reach of the sea, is an emblem of a new trend in fatalities. From 2013 to 2022, drowning from rainfall flooding, not storm surge, was the top cause of tropical-cyclone deaths, according to data from the National Hurricane Center—and the shift is already having profound effects. For individuals, this means reassessing established wisdom about hurricane safety. And American emergency-preparedness organizations, which have spent decades working to minimize fatalities from storm surge, haven’t fully adapted to combat the new leading killer.

As with any other major storm, Helene’s lethal nature was a product of numerous variables, assembled in just the wrong way. In North Carolina, there was simply too much rain all at once. A hot summer had saturated the air with moisture. Helene conjured rains in the area days before the massive cyclone arrived in the state, and merged with other storm systems, which resulted in even more rain. The mountains gave the storm winds an extra lift, sending moisture high up into the air, where it condensed and delivered still more precipitation. Remnant showers added to the total rainfall as the storm spun away.

[Read: ‘The death toll is going to be tremendous’]

Rainfall flooding is becoming deadlier than storm surge in part because of human-caused climate change, Michael Brennan, the director of the National Hurricane Center, told me. The warmer the ocean, the more moisture a hurricane can suck up. The warmer our atmosphere, the more moisture it can lend to a cyclone. Climate change may also be allowing storms to retain their strength farther inland than they would have otherwise—which means more of the U.S. might be vulnerable to the extreme rain they bring. “Anywhere it can rain, it can flood,” Brennan said. In the days since Helene, researchers have attempted to quantify climate change’s influence on the severity of the storm. One preliminary estimate, from Lawrence Berkeley National Laboratory, suggests that climate change may have caused up to 50 percent more rain to fall in some parts of the Carolinas and Georgia.

As Helene approached, North Carolinians expected rain and flash floods, but no mass-evacuation orders were issued. Buncombe County, home to Asheville and one of the worst-affected counties in North Carolina, relies on outdated flood maps from 2010 for its emergency planning, so officials may not have had the tools to appropriately warn residents in the highest-risk zones. And the mountainous, heavily wooded west of the state lacks the kind of evacuation infrastructure that is standard on the coast, including signage about exit routes. “Doing a mass hurricane evacuation right on the Gulf Coast is difficult enough, and there you have communities that have a cultural memory of evacuating,” says Samantha Montano, an emergency-management professor at the Massachusetts Maritime Academy and the author of Disasterology: Dispatches From the Frontlines of the Climate Crisis. When the rivers started overflowing and the rain kept coming, it was likely already too late to leave. The deluge weakened the soil, triggering cascading landslides that crumpled homes and roads.

[Read: Hurricane Helene created a 30-foot chasm of earth on my street]

Despite these failures of preparation, the response to the storm likely saved many lives. Hurricane Katrina, for example, claimed an estimated 1,400 lives in 2005 in part because of the federal government’s abysmal reaction. Compared with the Helene response, “it’s a night-and-day difference,” Montano told me. (Not every recent U.S. hurricane has resulted in appropriate aid: The federal government’s response to Hurricane Maria in 2017 was slow, and far too small in proportion to the destruction Puerto Rico suffered. About 3,000 people were killed.) Official decisions made before Katrina arrived also contributed to the casualty list: Despite alarming forecasts, New Orleans waited to issue evacuation orders until less than a day before the hurricane made landfall. And when the advisory went out, many residents of the city, which has some of the worst income disparities in the country, were unable to leave. Then, of course, New Orleans’s aging levees broke, submerging most of the city.

Storm-related deaths in the U.S., including from storm surge, have declined in recent decades, largely owing to advancements in forecasting and improvements in emergency management, Montano told me. But at the same time, a new threat has risen to the top. Meeting it, Brennan said, is “still a work in progress.” Updated flood maps are in the works in Buncombe County but won’t be ready until the end of next year. The National Weather Service, which houses the National Hurricane Center, has rolled out new flood-mapping services covering about 30 percent of the U.S., and expects to have data available for the entire country by 2026. In the meantime, Brennan said, evacuation notices should target people who live farther inland, who are at greater risk from hurricane weather than they might have been 40 years ago.

[Read: America needs a disaster corps]

Calculating the true toll of Helene’s wrath will take years. Hundreds of people are still missing. And official tallies don’t always factor in the deaths that follow in the months to come, caused by a shortage of drinkable water, electricity, and medical assistance. One study of U.S. tropical cyclones from 1930 to 2015, published yesterday, found that storms can contribute hundreds of additional deaths for as many as 15 years after they strike, because of stress, financial difficulties that prevent people from getting health care, and other long-term hardships.

The Southern Appalachian Mountains were supposed to be resilient against many effects of climate change. The area is cooler than other parts of the South. It is not usually subject to the winds that threaten coastal communities every time a hurricane comes through. But in the aftermath of Helene, the region has proved vulnerable to at least one danger that climate change is amplifying. It could not escape our moisture-laden skies or the fury they are poised to unleash.