The Trump administration Sunday ramped up its response to deadly Hurricane Harvey amid reports of Texas families trapped in their homes and a Weather Service pronouncement of "unprecedented" impacts — including up to 50 inches of rain predicted, and elevated highways under water.

Five people were reported killed by the deluge.

In Washington, President Donald Trump was headed into a late-morning Cabinet tele-conference on the disaster, tweeting "Even experts have said they've never seen one like this!"

Going to a Cabinet Meeting (tele-conference) at 11:00 A.M. on #Harvey. Even experts have said they've never seen one like this! — Donald J. Trump (@realDonaldTrump) August 27, 2017

Major rescue operations underway! — Donald J. Trump (@realDonaldTrump) August 27, 2017

The National Weather Service tweeted Harvey's impact was "unprecedented," adding "all impacts are unknown & beyond anything experienced."

While the weather bloggers, Texas Storm Chasers, warned "we could very well be watching the most disastrous flood event in US history unfold."

The federal government has 5,000 people on site in Texas and Louisiana, FEMA Director Brock Long said on CNN's "State of the Union" news program Sunday.

"FEMA is going to be there for years, sir," he said.

"This disaster will be a landmark event. And we're already in the stages – while we're focused on response right now and helping Texas respond – we're already pushing forward recovery housing teams."

Also on the program Texas GOP Gov. Greg Abbott said the federal government was giving the state "absolutely everything we need."

"We could not be more appreciative of what the federal government has done from the president on down," he said. "[E]verything we have asked for, they have given us."

On Fox News Sunday, Abbott added that he'd spoken with Trump and other Cabinet members, and that "[The] White House is being very responsive, very concerned about the people of Texas, and a tremendous help to us."

The Federal Emergency Management Administration deserved an "A plus, all the way to the president….all across the board, from the White House, to the federal administration to FEMA," he said.

Trump himself praised the coordination efforts for dealing with the flooding disaster that involved "thousands" of rescues.

In the Houston area, Coast Guard Capt. Kevin Oditt said helicopters have rescued more than 100 people in the Houston area as Tropical Storm Harvey floods numerous neighborhoods.

The storm made landfall Friday as a Category 4 hurricane before it was downgraded to a tropical storm.

But severe flooding has been ongoing in Houston and other towns in Southeast Texas, with 300,000 reportedly without power.

The Associated Press contributed to this report.