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Maps

Where Climate Change Will Bring Extreme Rainfall to the U.S.

By 2100, parts of the U.S. could see a 400 percent leap in extreme summer storms.

Cars lie in floodwaters after heavy rain undercut a road in Boulder, Colorado, in 2013. (NOAA)

The multiday storms that unleashed 6.9 trillion gallons of rain upon Louisiana this August wound up creating the worst U.S. natural disaster since 2012’s Superstorm Sandy. But while the catastrophic flooding might’ve seemed rare and shocking, such paralyzing deluges could become common by the end of the century if emissions continue at their current pace.

Now we know what parts of the country are likely to get slammed by such extreme rainfall, thanks to scientists at Boulder’s National Center for Atmospheric Research. Using computer simulations so comprehensive they took a year to run, researchers found that by 2100 many places around the U.S.’s Gulf and Southwest could see up to a 400 percent increase in the number of ultradrenching summer storms. Mexico is also facing a big uptick in extreme rains, and the risk is jacked up on Atlantic Coast and around the Rockies:

NCAR

In their investigation, the researchers assumed the world will be 9 degrees hotter by the end of the century, a consequence of taking no more action to cut emissions. Because a warmer atmosphere can hold more moisture, it’s plausible the storms of the future will not only be more frequent but more intense. Summer storms will probably deliver heavier rain-bombs over most of the country, the researchers believe, but especially in the Southwest and the Northeast where rain intensity could swell by 70 percent.

“These are huge increases,” NCAR‘s Andreas Prein says in a press release. “Imagine the most intense thunderstorm you typically experience in a single season. Our study finds that, in the future, parts of the U.S. could expect to experience five of those storms in a season, each with an intensity as strong or stronger than current storms.”

A street in Baton Rouge was turned into a river after extreme rains this August. (NOAA)

About the Author

  • John Metcalfe
    John Metcalfe is CityLab’s Bay Area bureau chief, based in Oakland. His coverage focuses on climate change and the science of cities.