(CNN) Tropical Storm Henri made landfall along the coast of Rhode Island near Westerly on Sunday as the slow-moving storm drenched the Northeast with heavy rain that could cause significant flooding.
Henri, which weakened from a Category 1 hurricane on Sunday morning, had sustained winds of 60 mph when it made landfall at about 12:15 p.m., the National Hurricane Center said. The storm is now a tropical depression, having weakened to 35 mph winds and slowed from 16 mph Sunday morning to 7 mph as of 8 p.m., the NHC said.
Still, the storm's damaging winds and dangerous storm surge could topple trees and power lines and cause flooding for millions of people across the region's major metropolitan areas. About 100,000 customers were without power in the Northeast, primarily in Rhode Island, according to Poweroutage.US.
Live updates: Tropical Storm Henri heads toward the Northeast
The slowing of the storm means it has dumped more rain on already-soaked areas and worsened the region's flood threat. Henri is expected to slow down further and may stall near the Connecticut-New York border Sunday night before turning to the east-northeast, the NHC said.
A flash flood warning is in effect until 11:45 p.m. Sunday for Morris, Sussex and northeastern Warren counties in New Jersey, according to the National Weather Service, and until midnight for Madison County in New York and Lackawanna County in Pennsylvania.
Tropical storm warnings in effect earlier Sunday were discontinued by 5 p.m., but the Weather Prediction Center has issued a moderate risk for excessive rainfall in parts of the Northeast for Monday into Monday night, including New York and much of central and southern New England.
A flash flood watch is in effect until Monday evening for parts of central New York and northeast Pennsylvania.
There's also a chance tornadoes may form Sunday over southern New England, CNN meteorologist Haley Brink said.
Henri has brought back difficult memories from 2012, when Superstorm Sandy -- a post-tropical cyclone -- made landfall in New Jersey with hurricane-force winds and devastated swaths of the Northeast.
The two storms are not the same, however.
"Henri is a much more compact storm than Sandy was when it made landfall," CNN weather producer Robert Shackelford said.
Even before landfall, the storm's outer bands brought record rainfall to New York City on Saturday night.
In Manhattan, Central Park set a daily record rainfall of 4.45 inches Saturday, the National Weather Service said. The heavy rain edged out the previous record of 4.19 inches dating back to 1888.
Between 10 and 11 p.m., 1.94 inches of rain fell in Central Park, setting the all-time NYC record for the most rain recorded in one hour, the National Weather Service in New York said. From Saturday to Sunday, more than 5 inches of rain have fallen in Central Park, making this the heaviest two-day rainfall total for this location since Hurricane Irene in 2011, according to the NWS.
Meanwhile, other areas in New York City saw 4 to 8 inches of rain, with Brooklyn receiving more than 6 inches in a 24-hour period.
Lightning in the city led officials to postpone the "WE LOVE NYC: The Homecoming Concert" in Central Park Saturday night, which was televised by CNN. The event was intended to celebrate New York City's progress in its fight against the Covid-19 pandemic.
Across the Hudson River, neighboring New Jersey saw rain totals of 1 to 3 inches in 24 hours.
Extreme rainfall rates such as this are becoming more common because of human-caused global warming, scientists say. A recent UN climate report stated, "the frequency and intensity of heavy precipitation events have increased since the 1950s over most land area."
New York officials closed all city beaches Sunday and Monday in anticipation of the storm's impact. New York City Mayor Bill de Blasio declared a state of emergency Saturday afternoon ahead of the storm, saying heavy wind, rain and storm surges are expected Sunday morning and urged everyone to stay indoors if they can. The mayor also issued a travel advisory, recommending residents limit travel Sunday, especially driving.
New York Gov. Andrew Cuomo warned people in flood-prone areas.
"If you know you are in an area that tends to flood ... get out of that area now, please," Cuomo said in a televised news briefing Saturday.
In advance of Henri, Cuomo declared a disaster for areas including Long Island, New York City, Westchester and Hudson Valley. New York has heavy equipment deployed on Long Island and water-rescue teams ready to go, Cuomo said.
Other parts of the Northeast similarly prepared for extreme weather and the potential for flooding and power outages.
Mandatory evacuations were ordered for the coastal towns of Guilford and Branford, according to a tweet from state Rep. Sean Scanlon.
"If you live in a coastal, low-lying or area prone to historic flooding due in Guilford, evacuate now. If you live in Zone 1 or 2 in Branford ... evacuate by 9pm," Scanlon wrote. "PLEASE TAKE THIS SERIOUSLY."
Rhode Island Gov. Dan McKee asked residents to stay home Sunday.
"I'm asking you, Rhode Island, to stay home until this storm passes. You are not only putting your own life at risk but you are endangering our first responders," McKee said during a news conference.
As resources from other states continue to pour in, McKee said he has ordered a ban on state roadways for motorcycles and tractor trailers, except those carrying emergency supplies. The governor said he is limiting access to a number of the state's bridges as well.
The National Guard in New York, Massachusetts, Connecticut and Rhode Island was activated or otherwise poised ahead of the storm to help with any rescues, cleanup and other support, officials said.
Eversource -- which provides electricity services in Massachusetts, New Hampshire and Connecticut -- set up 1,500 crews to help with power restoration efforts and 500 others for tree clean up.
The Edison Electric Institute, which represents companies that provide electricity for more than 220 million Americans, said 13,500 crews from at least 31 states, Washington, DC, and Canada are being positioned to move in after the storm.
"These crews will work around the clock to restore power as quickly as possible when and where they can, provided it is safe to do so," the institute said in a news release.