In a year full of extreme weather, experts say 2024’s spate of tornado outbreaks, in particular, set it apart.
From January through November (the latest month for which official counts are available), the U.S. recorded 1,762 tornadoes — the highest number in a decade, according to the National Oceanic and Atmospheric Administration.
The twisters tended to be strong and destructive, the records show, especially the unusually powerful tornadoes that spawned from Hurricane Milton in October.
“It was kind of like death by 1,000 paper cuts,” said Victor Gensini, a professor of meteorology at Northern Illinois University. “We didn’t have an unprecedented number of violent tornadoes, and there wasn’t a month with absolutely stellar activity — outbreak after outbreak after outbreak — but when you start aggregating them all together, what you get is a pretty significant year for severe weather.”
Tornado outbreaks were among the nation’s costliest weather and climate disasters this year. As of Nov. 1, NOAA had tallied a total of 24 weather disasters that each caused at least $1 billion in damage. Of those events, six were tornado outbreaks, including a cluster of storms over three days in July that produced more than 79 tornadoes across Illinois, Indiana, Minnesota, Pennsylvania and New York. An outbreak that hit Iowa in May also made the list — it spawned a devastating tornado that killed five people and cut a 44-mile path across the southeastern part of the state.
The flurry of tornado activity adds to an already sizable and growing set of concerns about the increasing frequency and severity of extreme weather. But unlike events like heat waves or wildfires, which have clear links to rising temperatures, researchers are still working to understand why this was such an exceptional tornado year, including possible connections to climate change.
Tornadoes are classified according to what’s known as the Enhanced Fujita (EF) scale. The weakest tornadoes, or EF-0 and EF-1, have winds of up to 110 mph and typically cause relatively light damage. The most powerful, or EF-5, have winds above 200 mph and usually cause catastrophic damage.
The tornado that flattened a swath of Iowa in May was an EF-4 tornado, and one of the deadliest of 2024. It tore through the town of Greenfield, tossing cars and ripping homes from their foundations. The twister was just one of more than a dozen that cut through the state that day. As a whole, the cluster of storms caused $4.9 billion in damage, according to NOAA.
This year, at least 52 people were killed in tornado outbreaks through November, according to preliminary figures from NOAA. While significant, the number pales in comparison to some of the country’s worst tornado years, when hundreds of people died. The single deadliest tornado in U.S. history was an EF-5 twister that killed 695 people in 1925.
The country was lucky to escape a high death toll in 2024, said Harold Brooks, a senior scientist at NOAA’s National Severe Storms Laboratory.
“There have been 27 killer tornadoes so far this year, and the most deaths out of a single event has been seven,” Brooks said. “It’s a little unusual to have that many killer tornadoes and not have any of them be a really big event.”
Still, the tornadoes that touched down caused extensive damage across some central and Southern states.
The July outbreak of more than 79 tornadoes caused $2.4 billion in damage. And a tornado outbreak in late May — separate from the one in Iowa — produced more than 110 tornadoes, including an EF-3 in Texas, causing a total of $3.4 billion in damage. In such cases, most of the damage is from winds that can be powerful enough to level buildings, warp utility poles and hurl debris far afield.
Several tornado events this year also surprised experts. One came just a couple of weeks ago, when a rare tornado touched down north of Santa Cruz, California. The twister injured five people; it was later classified as an EF-1 with peak winds of 90 mph. The storm prompted the National Weather Service to issue its first-ever tornado warning for San Francisco.
Another surprise was 2024’s considerable uptick in the occurrence of strong tropical tornadoes — tornadoes produced in hurricanes. Hurricane Milton, which pummeled western Florida when it made landfall on Oct. 9, produced dozens of destructive tornadoes across the state as the storm neared land.
Tornadoes are not altogether uncommon during hurricanes, but they are typically weaker than the ones observed in connection to Milton. Of all recorded tornadoes produced by tropical systems that have made landfall in the U.S., less than 1% have been EF-3 or stronger. This year, four of the five hurricanes that made landfall in the U.S. produced tornadoes of EF-3 intensity.
“Milton will likely go down as the most prolific tornado-producing hurricane in history,” Gensini said. “Those tornadoes rivaled what you would see in Texas, Oklahoma, Nebraska or the Great Plains. It’s highly unusual to see tornadoes of that strength and frequency with hurricanes.”
It’s not clear why Hurricane Milton churned out so many twisters, but a study published in June found that the number of tornadic storms could increase by as much as 299% by midcentury if fossil fuel emissions continue at their current pace.
However, scientists do not yet have a solid understanding of what influence, if any, climate change has on tornadoes overall. Thus far, research indicates that global warming can increase atmospheric instability, a key ingredient in the development of thunderstorms. Instability in the atmosphere often comes from differences in temperature and air density, which in turn fuels strong columns of rotating air within storms.
But many aspects of tornado science are still murky, including what causes some tornadoes to intensify while others break apart. Some studies have even found that climate change might suppress the formation of tornadoes by weakening vertical wind shear, a term that refers to the way winds increase and change direction at different atmospheric heights. Reduced wind shear could limit the amount of warm, rising air, making it less likely for storms to spawn tornadoes.
Given those lingering unknowns, teasing out any direct links between climate change and specific tornado outbreaks remains tricky.
“We do understand that greater instability and warmer temperatures should promote larger hail, more tornadoes and that sort of thing,” Gensini said. “But for any individual tornado, it’s very hard to make those assessments at this time.”
With several days left until the year ends, tornado outbreaks are still possible.
“This last quarter has been pretty quiet for tornadoes, but it’s not unheard of to have tornadoes — and perhaps even strong ones — in late December, in the cool season,” Gensini said.
Indeed, more twisters may be on the horizon: Severe storms and tornadoes are possible across parts of the South and Gulf Coast over the weekend, and NOAA’s counts for the year do not yet include tornadoes that were reported Thursday in Louisiana.