Harvey has spun deeper into Texas and unloaded extraordinary amounts of rain after the once-fearsome hurricane crashed into homes and businesses, leaving at least two people dead.
Throughout the region between Corpus Christi and Houston, many people feared that toll was only the beginning.
By 4am Sunday, the National Hurricane Centre said Harvey continued to cause “catastrophic flooding in south-eastern Texas”.
Harvey’s maximum sustained winds were about 45 mph, but the storm was practically stationary as it dumped torrential rain over an area that included Houston.
Authorities did not know the full scope of damage because weather conditions prevented emergency crews from getting into the hardest-hit places.
They dreaded the destruction that was yet to come from a storm that could linger for days and unload more than 40 inches of rain on cities, including dangerously flood-prone Houston.
In the island community of Port Aransas, population 3,800, officials were unable to fully survey the town because of “massive” damage. Police and heavy equipment had only made it into the northernmost street.
“I can tell you I have a very bad feeling and that’s about it,” said Mayor Charles Bujan, who had called for a mandatory evacuation but did not know how many heeded the order.
Some of the worst damage appeared to be in Rockport, a coastal city of about 10,000 that was directly in the storm’s path.
The mayor said his community took a blow “right on the nose” that left “widespread devastation,” including homes, businesses and schools that were heavily damaged. Some structures were destroyed.
Rockport’s roads were a mess of toppled power poles. A trailer blocked much of one major intersection. Wood framing from ripped-apart houses was strewn along Route 35 on the town’s southern end.
Harvey’s relentless wind tore the metal sides off the school gym and twisted the steel door frame of its auditorium.
“We’re still in the very infancy stage of getting this recovery started,” said Aransas County spokesman Larry Sinclair.
One person was killed in Aransas County in a fire at home during the storm, county Judge C.H. “Burt” Mills Jr said. A second person died in flooding in Harris County, where Houston is located.
Mr Mills also said as many as 14 people suffered minor injuries in his county, including slips and falls, scrapes and a broken leg.
In Houston, authorities were pleading with people not to leave their homes as a flood emergency was declared.
“The streets are treacherous,” Houston mayor Sylvester Turner said.
The fiercest hurricane to hit the US in more than a decade came ashore late Friday about 30 miles northeast of Corpus Christi as a mammoth category four storm with 130 mph winds.
Harvey weakened to a tropical storm by midday Saturday.
The hurricane posed the first major emergency management test of President Donald Trump’s administration.
Mr Trump met his Cabinet and other senior administration officials to discuss the federal response to the damage and flooding, the White House said Saturday in a statement.
The president held a video conference from Camp David in which he instructed departments and agencies to “stay fully engaged and positioned to support his number one priority of saving lives”, the statement said.