Why Flash Floods Are Surging Across the U.S. This Summer, According to Scientists

This summer has marked a terrifying shift in the American weather pattern: from coast to coast, catastrophic flash floods have surged, upending lives and communities. Scientists say it’s no coincidence — climate change is intensifying the severity and frequency of these deadly rain events.

Record levels of moisture in the atmosphere, fueled by warming oceans and hotter air temperatures, have set the stage for what experts call “100-year” or even “1,000-year” floods. These events, which historically had just a 0.1% annual chance of occurring, are now happening in multiple states within days of each other.

The recent flooding began with a devastating event in Texas on July 4 that killed over 130 people. Within days, deadly flash floods struck New Mexico, Chicago, North Carolina, New York City, and most recently Kansas City — many of them fueled by unprecedented rainfall levels.

Daniel Swain, a climate researcher at UCLA, explained that this summer’s weather patterns have funneled warm, humid air from the Gulf of Mexico and the Atlantic, creating record-breaking atmospheric moisture across much of the U.S. “It’s like wringing out a soaked sponge,” he said.

The physics of these rain events is simple but alarming. Warmer air holds more water vapor, and warmer ground pushes moist air upward — leading to powerful thunderstorms and torrential downpours. “This is almost a textbook example of climate change impacts,” said climate scientist Kate Marvel.

Michael Mann of the University of Pennsylvania adds that human-caused warming isn’t the only factor. Atmospheric resonance — a phenomenon where weather patterns get “stuck” — has become three times more frequent since the mid-20th century. These stagnant systems can dump rain over the same areas for days, greatly increasing the risk of flooding.

The bottom line? While average rainfall might not drastically change, extreme rainfall — the kind that leads to flash floods — is getting worse and more common due to global warming.

“This summer’s floods are not just random,” said Marvel. “There is absolutely no doubt that climate change, caused by human emissions of greenhouse gases, is making extreme rainfall more extreme.”

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