Extreme Precipitation Events Have Risen Sharply in Northeastern U.S. Since 1996

Episodes of heavy rainfall in the U.S. Northeast have increased dramatically since 1996, with the most extreme storms coming in the spring and fall, according to a new study.


Analyzing rainfall data from 1901 to 2014, researchers at Dartmouth College found that from 1996 to 2014, incidents of extreme precipitation in the Northeast were 53 percent higher than from 1901 to 1995. The number of storms that produce extreme precipitation — defined as two or more inches of rain in 24 hours — has been steadily increasing since 1901, but the researchers said the increase since 1996 has been abrupt. With a few exceptions, the jump in heavy rain events has been relatively uniform across the Northeast, which the researchers defined as a 12-state region from Maine to West Virginia.

The change is most likely linked to rising temperatures, since warmer air holds more moisture, which can affect the frequency and intensity of rainfall. The research, published in the Journal of Hydrometeorology, said that heavy rainfall events in the spring and fall were 84 percent more common from 1996 to 2014 than from 1901 to 1995. The scientists said their future research would focus on what is driving the sharp increase in extreme precipitation.