The National Weather Service in Boston said that looking at radar data and videos it appears likely that a tornado toppled trees and knocked down power lines in Rhode Island and Connecticut on Wednesday. Rob Megnia, a meteorologist with the weather service, said they received reports of about 20 trees down in Killingly, Connecticut, and trees and power lines down in Foster, Rhode Island.

The agency said it would survey the storm damage in both states on Thursday to help determine the tornado’s strength, maximum wind speed and its path.

Emergency sirens could be heard late Wednesday afternoon in parts of Providence, Rhode Island, as cellphones pinged with a tornado warning. In Lincoln, Rhode Island, photos after the storm showed at least one roof damaged, a trampoline blown into some trees and the press box at the high school stadium tipped into the bleachers.

The weather service also issued a flash flood warning for parts of Connecticut until 9:45 p.m.

In North Attleborough, Massachusetts, which was hit by heavy flooding Monday night, Sean Pope was watching the forecast with unease.

Heavy rains had turned his swimming pool into a mud pit and filled his basement with 3 feet of water. He has been able to get the power back on in the first and second floor of the home he shares with his wife and three children, but he worried about more flooding.

“I am hanging on, hoping and watching the forecast and looking for hot spots where it may rain and where there are breaks,” he said. “It’s raining really hard again so we have to make sure the pumps are working.”

Elsewhere in the state, Leominster resident Zac Brown was still cleaning up his home and backyard Wednesday after flood waters from a nearby stream flooded his basement, washed away part of his retaining walls and dumped rocks, boulders and other debris in his backyard.

He remembers his frantic efforts to survive the floods, including rushing to shut down the power, knocking on roommates’ and tenants’ doors and telling them to leave. While he built a “blockade” of cement bags, he said there wasn’t much he could do if more rain came.

“I have no physical attachment to the house, so if it goes, it goes and that’s what God wants, and if it doesn’t, it doesn’t and that’s awesome,” Brown said.

Late Tuesday, Massachusetts Gov. Maura Healey issued a state of emergency following the “catastrophic flash flooding and property damage” in two counties and other communities. The 10 inches of rain over six hours earlier in the week was a “200-year event,” said Matthew Belk, a meteorologist with the National Weather Service in Boston.

Healey said Wednesday that while there aren’t plans to call up the National Guard, the state’s emergency management agency is keeping a close eye on the weather and is prepared to offer assistance.

She said the state is monitoring the conditions of dams in many communities and urged residents to take seriously any flood warnings and to stay off the roads when ordered.

“Something that looks pretty minor can, just within a couple of hours, turn into something very serious, potentially deadly and very, very destructive,” Healey said.

The rain created several sinkholes in Leominster, Massachusetts, including one at a dealership where several cars were swallowed up. In Providence, Rhode Island, downpours flooded a parking lot and parts of a shopping mall. Firefighters used inflatable boats to rescue more than two dozen people stranded in cars.

Parking lots at several businesses briefly became lakes in Leominster and North Attleborough, and many front yards were still partially covered in water. The sounds of generators filled the air in many neighborhoods, as residents worked to remove water from their basements.

John DeCicco, a retired school teacher in Leominster who loaned generators to neighbors, said residents of the close-knit community about 40 miles (65 kilometers) northwest of Boston were helping each other clean up and opening their homes to others whose residences are uninhabitable.

Dawn Packer, who runs a North Attleborough home preschool, had looked across the street Monday evening to see a UPS truck floating in several feet of water. Soon her yard was flooding.

“All of sudden, the door smashed open. The water was so forceful. It just smashed the door open and poured in, 4 feet,” she said.

After a dry day, it started raining in Leominster again Wednesday afternoon. Parts of Massachusetts and Rhode Island were under a flash flood warning. Earlier in the day, there were heavy downpours in Danbury, Connecticut, where officials said they had to rescue several people from vehicles stuck in floodwaters.

“The ground is saturated. It can’t take in anymore,” Leominster Mayor Dean Mazzarella said at a news conference Wednesday. But he said the city had emergency resources at the ready “for whatever the weather brings.”

Mazarella said up to 300 people were evacuated by Tuesday morning in the city, which has not seen such widespread damage since a 1936 hurricane. Most buildings downtown flooded and some collapsed. He said the city was trying to help get assistance to homeowners and businesses that suffered damage. He said early estimates on city infrastructure restoration projects could be anywhere from $25 million to $40 million.

New England has experienced its share of flooding this summer, including a storm that dumped up to two months of rain in two days in Vermont in July, resulting in two deaths. Scientists are finding that storms around the world are forming in a warmer atmosphere, making extreme rainfall a more frequent reality now. A warming world will only make that worse.