A monster. A beast. Catastrophic. Vicious.

Hurricane Florence is all of the above – and more, according to meteorologists, who predict the powerful slow-moving Category 4 whirlwind that’s set to crash into the Carolinas by week’s end could go down as “the storm of a lifetime” for this part of the East Coast.

Mandatory evacuation orders are in place for the low-lying coastal areas of North Carolina, South Carolina and Virginia, affecting more than 1 million residents and tourists – though not everybody is heeding the warnings of local authorities.

On Tuesday, President Donald Trump promised the federal government’s support, saying that the U.S. was “as ready as anybody’s ever been,” but urged people in mandatory evacuations areas to get out now – even if they’ve successfully weathered past hurricanes.

“They haven’t seen anything like what’s coming at us in 25, 30 years – maybe ever,” Trump said.

“This will likely be the storm of a lifetime for portions of the Carolina coast,” warned the National Weather Service in Wilmington, North Carolina.

Florence is now on a more southerly track and is expected to slow down considerably by late Thursday into Friday and move slowly through early Saturday, the National Hurricane Center said Wednesday. The center will approach the coast of North Carolina or South Carolina in the hurricane warning area on Thursday and Friday, the center said.

Here are three reasons why Hurricane Florence is such a danger:

Storm surge

When Florence makes landfall, it will bring a wall of water that could reach 20 feet tall, wrote Weather Underground meteorologist Jeff Masters.

How serious is the storm surge? The National Hurricane Center lists any storm surge over 12 feet as “life-threatening,” the center’s director, Ken Graham, told CNN.

“Large, battering waves will ride atop this surge,” The Weather Channel reported.

The National Hurricane Center predicted storm-surge inundations up to 13 feet in some areas of Florence’s path.

Wind

Florence will pack a punch, delivering the power to structurally damage buildings, knock down power lines and topple trees. Winds will reach tropical storm strength on Thursday near the Carolinas; hurricane conditions are expected to reach the coast on Friday.

The extreme winds can also transform furniture, decorations and other debris into flying projectiles, the division chief for Durham Emergency Management, Leslie O’Connor told CBS 17 in Raleigh, North Carolina.

“Anything that gets picked up by wind becomes a projectile, and it could also become a life-safety hazard,” O’Connor said.

Inland rain

The rainfall predictions are staggering, potentially up to 35-40 inches in some isolated areas, the Weather Channel reported, and the dangers will intensify if the storm – as projected – stalls over the Carolinas.

After Harvey made landfall last year near Corpus Christi, the storm stalled over Houston, drenching the metro area with as much as 5 feet of rain.

“It will be worse than a Harvey in the sense that the terrain is not like Houston, which is flat. If you put 2, 3, 4 feet of rain over flat ground, you have a certain kind of problem,” Weather Channel expert Bryan Norcross said. “But if you put a foot or 2 – or maybe in some isolated places more – of rain over hills and mountains, you have a very different kind of problem, which is really more dangerous than the flat situation, as bad as that was.”

If Florence stalls, the Weather Channel predicted “disastrous flooding” across areas that experienced especially wet summers, according to the National Oceanic and Atmospheric Administration.

Interactive Storm Tracker