A flash flood is a rapid rise of water along a stream or in a low-lying urban area, the National Weather Service said. Flash flooding can result from slow-moving thunderstorms, from numerous thunderstorms that develop repeatedly over the same area, or from heavy rains associated with tropical cyclones.

A flash flood warning is in effect until 9 a.m. for Boston and several communities south of the city, including Brockton, Quincy, and Randolph, officials said Thursday morning. The National Weather Service also issued a flood watch that will remain in effect until 4 p.m. for Rhode Island and eastern portions of Massachusetts and Connecticut.

Back-to-back flooding disasters in recent years — in Texas, New Mexico and Kentucky, among many others — have showed that preparing for flash flooding is a new necessity as the planet warms.

Recent flash flooding in Texas​, New Mexico​ and North Carolina​ is highlighting the extreme danger of these natural disasters and the need to be prepared.

At 12:38 a.m. on Thursday, the NWS Raleigh NC issued an updated flash flood warning in effect until 2:30 a.m. for Wake County.

Flash flooding has been in the spotlight in the last week, with several record breaking flood events occurring nearly back-to-back across the country. CNN’s Tyler Ory explains why they’re becoming more intense .

As crews search for missing people after flash floods killed at least 120 in Texas, cities across the U.S. grapple with rising flood waters.

Thursday's rain was a highly localized event. The highest impact was only felt over a 5-to-10 mile area south of Boston.