National Grid said it is deploying over 4,000 personnel in Rhode Island and Massachusetts to restore power to affected areas.

As of 5 p.m. Sunday, approximately 72,600 customers in Rhode Island and 8,500 in Massachusetts were without power, according to the utility.

"The hardest hit communities in Rhode Island include South Kingstown, Narragansett, Westerly, Jamestown, Charlestown and North Kingstown," National Grid said in a news release.

The utility said it estimates to have power restored to all affected customers by mid-week.

Tropical storm warnings for the Northeast states affected by Henri were dropped around 5 p.m Sunday.

However, 40 million Americans across nine states from Delaware to New Hampshire remain under a flash flood watch as the threat for major flash flooding continues through Monday.

Rainfall rates of two inches and hour have been reported in areas experiencing flash flooding, and an additional half a foot of rain is still forecast with highest amounts likely over the Lower Hudson Valley, Northeast New Jersey, New York City, Connecticut and western Massachusetts.

-ABC News' Melissa Griffin

President Joe Biden updated Americans on the federal government's response to Tropical Storm Henri.

Biden reiterated that he has approved the state of emergency orders declared in Rhode Island, Massachusetts and New York and said the Federal Emergency Management Agency is ready to help affected communities.

He said thousands of live crews from the agency are already on their way.

"They'll clean up fallen trees, help local utilities repair damaged lines and restore service as fast as possible," Biden said at his news conference.

Biden warned that the storm is still causing flooding and reminded affected residents to prepare for more damage throughout the coming days.

As of 4:10 p.m., there are at least 121,993 customers without power in five states, according to PowerOutage.US, a site that aggregates power outage reports.

Rhode Island has the most power outage numbers with 75,868, followed by Connecticut,  29,776, Massachusetts, 9,205, New Jersey, 4,009 and New York, 3,135.

Connecticut Gov. Ned Lamont warned about the potential flood risk and outages posed by Hurricane Henri, which is expected to bring significant rainfall and winds to western Connecticut.

During a press briefing Saturday, Lamont said the Category 1 storm could be especially severe due to the combination of 8 inches of rain forecast on top of saturated soil, winds and an "astronomical tide."

Winds up to 80 mph also pose a danger to utilities, with "hundreds of thousands of outages over the next few days and beyond" anticipated, Lamont said. EverSource, Connecticut’s largest electric provider servicing approximately 1.25 million customers, is preparing for between 50% and 69% of its customers to lose power. Restoration efforts "could last between eight and 21 days," the company said in a statement.

The state is making sure there is stand-by power available for cooling centers and has worked with utility companies on "a lot of tree trimming" to limit the number of vulnerable trees, Lamont said. The state has also activated 200 National Guard members.

"We are prepared for what should be a tough storm," Lamont said.