Hurricane Florence has killed a mother and child in North Carolina.

The Wilmington Police Department said the two were killed when a tree fell on their house on Friday. The father was transported to a hospital for treatment.

North Carolina’s governor’s office said a third person was killed while plugging in a generator.

The hurricane came ashore early on Friday, pounding the state with torrential rain and high winds.

Forecasters have been predicting catastrophic flash flooding. The National Hurricane Centre in Miami says more than 16 inches of rain has fallen at locations in southeast North Carolina and another 20 to 25 inches is on the way.

The hurricane has torn buildings apart and knocked out power to more than 600,000 homes and businesses.

More than 60 people had to be pulled from a collapsing motel and hundreds more were rescued elsewhere from rising water.

“We are coming to get you,” the city of New Bern tweeted around 2am local time. “You may need to move up to the second story, or to your attic, but we are coming to get you.”

The giant, 400-mile-wide hurricane unloaded heavy rain, flattened trees, chewed up roads and knocked out power to more than 600,000 homes and businesses.

Forecasters say the biggest danger is the water as the storm surge along the coastline and the prospect of one to three-and-a-half feet of rain over the coming days could trigger catastrophic flooding inland.

By early afternoon, Florence’s winds had weakened to 75mph, just barely a hurricane and well below the storm’s terrifying Category 4 peak of 140 mph earlier in the week.

But the hurricane had slowed to a crawl as it traced the North Carolina-South Carolina shoreline, drenching coastal communities for hours on end.

The town of Oriental had taken more than 18 inches of rain just a few hours into the deluge, while Surf City had 14 inches and it was still coming down.

“Hurricane Florence is powerful, slow and relentless,” North Carolina governor Roy Cooper said. “It’s an uninvited brute who doesn’t want to leave.”

Cooper said the hurricane was “wreaking havoc” on the coast and could wipe out entire communities as it makes its “violent grind across our state for days”.

He said parts of North Carolina had seen storm surges — the bulge of seawater pushed ashore by the hurricane — as high as 10 feet.

Florence made landfall as a Category 1 hurricane at 7.15am at Wrightsville Beach, a few miles east of Wilmington and not far from the South Carolina line, coming ashore along a mostly boarded-up, emptied-out stretch of coastline.

It was expected to begin pushing its way westward across South Carolina later in the day, in a watery siege that could go on all weekend.

For people living inland in the Carolinas, the moment of maximum peril from flash flooding could arrive days later, because it takes time for rainwater to drain into rivers and for those streams to crest.

Preparing for the worst, about 9,700 National Guard troops and civilians were deployed with high-water vehicles, helicopters and boats that could be used to pluck people from the floodwaters.

Authorities warned, too, of the threat of mudslides and the risk of environmental havoc from floodwaters washing over industrial waste sites and hog farms.

Meanwhile, forecasters have warned that Storm Helene could pose a danger to life when it bears down on the UK and Republic of Ireland next week.

Ferocious winds lurking in the Atlantic threaten to whip across western regions of England and Wales from Monday evening, heralding a day of disruption and hazardous conditions.

Helene is among a glut of tropical storms brewing in the region, with mass evacuations under way in southern US states as Florence barrels across Virginia and the Carolinas.

The Met Office issued two “yellow” alerts on Friday as the storm began creeping towards south-western corners of the UK and the tip of Ireland.