After the heaviest rainfall in a decade, residents waded through waist-high water on washed out roads, some paddling to swamped homes in canoes, and meteorologists forecast more rain in all three New England states, which have declared states of emergency.
"I've never seen flooding like this before," said Faustino Melo, 40, a resident in the hard-hit Massachusetts city of Peabody, a suburb north of Boston whose downtown streets were submerged with floodwaters that rose as high as door handles.
Emergency crews steered boats along streets to help evacuate people, while National Guard soldiers set up checkpoints to block off roads. About 200,000 sand bags were used to hold back overflowing rivers across Massachusetts.
About 30 to 38 cm of rain has fallen since Friday, swelling the Merrimack River that runs through southern New Hampshire and Massachusetts more than 2.4 metres above flood stage - its highest since 1936.
"It's bad now but we're expecting it to get much much worse," said Massachusetts Emergency Management Agency spokesman Peter Judge, citing weather forecasts for more rain tonight with several rivers still rising.
"Right now we're looking at all of the rivers, from the Charles River in the Boston area all the way north and east to the Merrimack River on the New Hampshire border. We expect all of those rivers to reach and exceed flood stage in the next 24 hours," Judge said.
Several thousand New Hampshire residents had been evacuated from homes and more than 600 roads in the state had been closed, the New Hampshire Bureau of Emergency Management said.
A bulging dam in Milton, New Hampshire on the Maine border was in danger of failing and could send a three-metre wall of water downstream, the National Weather Service said.
About a thousand people were evacuated from their homes in the
Massachusetts' suburbs of Melrose, Haverhill, Lawrence and Peabody, where flooding caused sewage to back up into cellars and sinks, rescue workers said.
No injuries or power outages were reported as of today, partly because no strong winds accompanied the storm.