Dangerous flash floods stranded motorists and left roadways under water. Some outdoor activities were canceled as communities scurried to keep pace with the rising waters.

Heavy rainfall caused areas of flooding on I-93 and other major roadways in Massachusetts on Thursday morning.

BRAINTREE, Mass. — Drenching downpours quickly turned highways and streets in eastern Massachusetts into rivers, just as traffic started to build for the Thursday morning commute. A large part of Interstate 93 in the Milton-Quincy area was underwater before 7 a.m. as torrential rain moved through.

Mayor Lynn Crawford said hearts are broken over the lives lost and stomachs are in knots as residents begin to take stock of the damage.

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.

It’s really hard to comprehend, but it does kind of put into perspective making sure all of our safety protocols and things like that are in place to make sure we are doing our very best to keep campers and out staff safe every single day.

Local officials in one of the hardest-hit counties have still revealed little about what, if any, actions they took to safeguard residents, tourists, and visitors in an area known as “flash flood alley.

Heavy rain moved through parts of eastern Massachusetts, causing flash flooding along I-93 on Thursday morning.