U.S. tropical cyclones, including hurricanes, have been linked to thousands of deaths for nearly 15 years following a storm. Researchers suggest that an average tropical cyclone in the U.S. results in 7,000 to 11,000 excess deaths. Overall, since 1930, these storms have contributed to an estimated 3.6 million to 5.2 million deaths in the U.S., surpassing fatalities from motor vehicle accidents, infectious diseases, or military conflicts in the same timeframe.
Recent research indicates that hurricanes and tropical storms in the United States lead to a significant increase in deaths for nearly 15 years post-storm.
Government statistics typically only account for the people who die during these storms, collectively known as “tropical cyclones.” Direct deaths, which average around 24 per storm according to official figures, usually happen due to drowning or trauma. However, a new analysis published on October 2 in Nature uncovers a greater, hidden death toll that emerges after storms.
“Every month, people are dying sooner than they would have if the storm had not struck their community,” said Solomon Hsiang, lead author and professor of environmental social sciences at the Stanford Doerr School of Sustainability. “When a major storm hits, it triggers a series of effects such as city rebuilding, displacement of families, and disruption of social networks. These outcomes can have serious public health implications.”
Hsiang and lead author Rachel Young estimate that an average U.S. tropical cyclone leads to an excess of 7,000 to 11,000 indirect deaths. They have calculated that since 1930, tropical storms have resulted in between 3.6 million and 5.2 million deaths in the U.S., far exceeding the approximately 10,000 deaths reported by official statistics.
Underestimating hurricane impacts
The revised estimates derive from a statistical analysis of 501 tropical cyclones that struck the Atlantic and Gulf coasts between 1930 and 2015, along with mortality rates for various populations in each state before and after these tropical events. This research expands on earlier studies, including a 2014 investigation by Hsiang that linked tropical cyclones with economic downturns lasting 15 years, and a 2018 Harvard study which concluded that Hurricane Maria caused nearly 5,000 deaths in Puerto Rico shortly after the storm—almost 70 times the official government figures.
“Initially, we expected to see a delayed mortality effect from tropical cyclones for perhaps six months or a year, similar to what happens with heat waves,” stated Young, a postdoctoral researcher at the University of California Berkeley, where she worked on the study during her master’s research in Hsiang’s lab before he joined Stanford’s faculty in July 2024. Results show that deaths related to hurricanes persist at higher rates not just for months, but for years after the storm has passed and the floodwaters have receded.
Disparity in health impacts
The findings by Young and Hsiang represent the first evidence that hurricanes significantly influence the distribution of overall mortality risk across the U.S. While the study indicates over 3% of all deaths nationally are tied to tropical cyclones, certain demographic groups bear a disproportionately higher burden, with Black individuals being three times more likely to die post-hurricane than white individuals. This underscores longstanding concerns raised by many Black communities regarding the unequal treatment and challenges faced after natural disasters.
The researchers estimate that 25% of infant deaths and 15% of fatalities among individuals aged 1 to 44 in the U.S. link to tropical cyclones. For these demographics, the additional risk from these storms significantly elevates overall mortality rates due to their already low baseline mortality rate.
“Some of these infants are born long after a tropical cyclone, meaning they couldn’t have experienced the event in utero,” Young noted. “This highlights a broader narrative involving prolonged economic and maternal health disadvantages, where mothers may lack essential resources years after facing a disaster compared to a scenario without a tropical cyclone.”
Preparing for future risks
The gradual increase in cyclone-related deaths is much more pronounced in areas that historically encounter fewer hurricanes. “Since this extended mortality effect hasn’t been documented before, neither those on the ground nor the medical community have been adequately prepared to respond,” Young explained.
The findings from this study could guide government and financial decisions regarding climate change adaptation strategies, enhancing coastal resilience, and improving disaster management, especially as tropical cyclones are expected to intensify due to climate change. “With climate change, we foresee that tropical cyclones may grow more dangerous, more destructive, and their impacts could shift,” added Young.
Pursuing solutions
Building on the findings from the Nature study, Hsiang’s Global Policy Laboratory at Stanford is currently investigating the reasons behind the prolonged mortality effects of tropical storms and hurricanes over a 15-year period. The research team employs a blend of economics, data science, and social sciences to tackle vital policy questions about managing global resources, primarily those linked to climate change impacts.
For mortality risks associated with hurricanes, the main challenge is to untangle the complex chain of events that follow a cyclone, which ultimately can affect human health, while also assessing potential interventions.
These events can be far removed from the original disaster, often making it difficult for affected individuals and families to correlate the two. For instance, Hsiang and Young suggest that individuals might deplete their retirement savings to fix property damage, which subsequently limits their funds for future health care. Relatives might relocate, weakening support networks crucial for maintaining good health. Additionally, public funds may prioritize urgent recovery over long-term investments beneficial for health.
“Some solutions could be quite straightforward, such as advising families and policymakers that a few years after allocating recovery funds, it might be wise to consider additional savings for health care expenses, particularly for vulnerable populations like the elderly, communities of color, and mothers or expectant mothers,” Young concluded.
