EDITOR’S NOTE: In a bit of unusual timing, a new Dartmouth study of precipitation has found that climate change is causing the Northeast to have less frequent and less intense droughts. The timing is interesting because we’re currently in a mild drought, with portions of coastal Maine facing moderate to extreme drought.
As climate change continues to impact the U.S., many regions throughout the country, especially the West, are experiencing more drought. But over the last century, the Northeast has experienced something different—less frequent and less intense droughts due to increased precipitation, according to a new Dartmouth study.
The findings are published in the Journal of Hydrometeorology.
“In the Northeast, we have warming temperatures, which means we lose more water from the surface, but we have also had increasing precipitation,” says lead author Jonathan Winter, an associate professor of geography and director of the Dartmouth Applied Hydroclimatology Group, whose work has explored extreme precipitation changes in the region.
“It’s a tug-of-war between how fast precipitation is increasing and how fast evapotranspiration—the loss of water from plants and soils—is increasing.”
The research team assessed changes in monthly drought from 1901 to 2022 over the Northeast—Connecticut, Delaware, Maine, Maryland, Massachusetts, New Hampshire, New Jersey, New York, Pennsylvania, Rhode Island, Vermont, Washington, D.C., and West Virginia—using temperature and precipitation station data from the National Oceanic and Atmospheric Administration.
To examine changes in drought across the region, the team analyzed the intensity, frequency, variance, and duration of drought. Using temperature, precipitation, radiation, and soil data, they calculated the Palmer Drought Severity Index—a metric used to measure drought.
The researchers compared their results to the U.S. Drought Monitor—a weekly map identifying areas in drought—which is used to determine payouts for crop insurance.
They also compared their findings to changes in soil moisture. Given that soil moisture measurements across the region are limited, the team used modeled soil moisture, which blends a climate model with observational data.
The findings show that across all months, drought was 59% less frequent and 19% less intense from 1984 to 2022 as compared to 1901 to 1983. Results were similar in the warm season (June-November) when drought has the largest impacts; warm season drought frequency and intensity decreased by 56% and 16%, respectively.
The results also demonstrate that as of 1984, the Northeast was statistically wetter relative to the earlier period.
Swings between monthly wet and dry events have not changed, demonstrating that the Northeast has not experienced more “weather whiplash,” or alternating floods and droughts.
To determine the potential drivers of reduced drought, the researchers ran their analysis again but fixed temperature at historic levels while letting precipitation increase, and vice versa. They found that precipitation increases are responsible for the observed reductions in drought.
“As long as increases in precipitation continue to outpace increases in evapotranspiration, more drought in the Northeast is unlikely,” says Winter. However, climate models vary on whether this trend will continue in the future.
“The Northeast has always had, and will continue to have, droughts,” says co-author Erich Osterberg, a professor of Earth and planetary sciences. “A year ago, over one-third of the Northeast experienced severe or extreme drought, with major impacts on farmers and water supplies.”
“The good news is that these damaging droughts have become less common and less severe due to more rainfall,” says Osterberg. “The bad news is that the higher rainfall has increased the frequency and impacts of severe floods.”
Janelle Wargo, Guarini ’25, and Justin Mankin, a professor of geography, also contributed to the study.