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Late last month, Hurricane Helene drenched the Southwest United States. Devastating floods hit communities on the Gulf Coast and southern Appalachia. The storm killed more than 200 people and destroyed billions of dollars of property.

As relief efforts begin to put the pieces back together, many are left wondering if the norms of extreme weather in America have changed. Was this unprecedented storm a freak occurrence or a new precedent?

Albert Kettner is the associate director of INSTAAR and the director of the DFO Flood Observatory (formerly the Dartmouth Flood Observatory). Since he took over the observatory in 2019, Kettner has tracked precipitation, drought and flooding around the world. His observations are built on the foundations laid by INSTAAR Senior Research Scientist Robert Brakenridge, who founded the observatory in 1993.

According to Kettner's data, extreme floods like the ones that hit Appalachia last month have become more common in the 21st century.

It's not the case that the world is getting wetter. In fact, many places are becoming more arid. Rather, really big floods, which were previously rare, are happening more often.

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