From flash drought to flash floods: Northeast endures weather whiplash
In May, drought developed across parts of the Northeast due to a combination of weather factors. Less than two months later, extreme rainfall in July led to dangerous flooding in some locations — and the month was ranking among the wettest on record for some.
At the end of May, parts of the Northeast were on the brink of a flash drought, or bouts of short-term drought fueled by weather conditions. Lower-than-average rainfall, high temperatures, strong winds and increased sunlight caused abnormally dry and drought conditions to develop across the region.
Now, less than two months later, the same region is under threat of flash flooding.
In May, the driest conditions were in eastern Pennsylvania. Philadelphia’s historical average for rainfall in May is 3.89 inches, but this year only 0.24 of an inch was recorded — barely 7% of the usual amount, according to National Weather Service (NWS) data.
A driver stops on a mud-covered bridge while deciding whether to drive through flood waters of the Winooski River, Wednesday, July 12, 2023, in Montpelier, Vt. The driver decided to back up, following a storm that dumped nearly two months of rain in two days. Vermonters are cleaning up from the deluge of water. (AP Photo/Charles Krupa)
But in July, Philadelphia has been thoroughly soaked. The city has recorded 3.85 inches of rain so far this month according to the NWS, well above the historical average of 2.52 inches through July 19.
Back on June 6, areas of moderate drought, as well as abnormally dry soil conditions, were more widespread across the Northeast. In fact, all of Pennsylvania was either dealing with abnormally dry or moderate drought conditions at the time. But as of July 18, about 40 percent of the state was completely free of drought.
Much of New England and New York state have also seen a notable improvement in drought conditions, although pockets of drought still persist across parts of the region.
In New York, cities are experiencing unprecedented levels of rainfall. This month is already the second-wettest July on record in Albany, New York, which recorded 9.41 inches of rainfall with almost half the month left to go, according to the NWS. Historically, the city has only recorded 2.75 inches of rain by this point of the month.
Albany has measured enough precipitation for this month to rank among the wettest Julys on record as of July 19, 2023.
Cities in New England have also been wetter than average, with some places experiencing top-five July precipitation amounts. Worcester, Massachusetts, has experienced a particularly dramatic deviation in rainfall this month, recording 9.89 inches of rain so far, according to the NWS. This number would qualify this month as the city’s fourth-wettest July on record.
The historical rainfall average for the city in July would be 3.93 inches, which means Worcester is seeing more than two times as much rain as the average.
Worcester has measured enough precipitation for this month to rank among the wettest Julys on record as of July 19, 2023.
The increased rainfall has meant the dangers of flash floods have plagued the Northeast in the first few weeks of July. Vermont suffered the state’s worst flood in over 100 years that brought many of the state’s dams to capacity.
As of July 18, 2023, there have been 44 fatalities related to floods in the United States, according to NWS data, with 10 of these deaths being reported in July. Most of these deaths — 32 — happened when the victim was driving, according to the NWS.
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Floods killed 102 people in the U.S. in 2022, with almost half — 48 deaths — being reported in July.
Experts warn that flash floods can happen minutes to hours after a period of excessive rainfall or a sudden release of water from a dam failure or ice jam, according to the NWS. In addition to forming rapidly, flash floods also move quickly and powerfully. Just 6 inches of moving water could easily knock a person off their feet or stall a car by sucking water into the tailpipe. If the water reaches a foot deep, the NWS says it can sweep away most vehicles.
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