National Weather Service Director Louis Uccellini says Hurricane Irma is so record-breaking strong it's impossible to hype.
Uccellini told The Associated Press on Wednesday he's concerned about Florida up the east coast to North Carolina, starting with the Florida Keys.
He warns that "all the hazards associated with this storm" are going to be dangerous.
Hurricane expert Kerry Emanuel of MIT calculates that Irma holds about 7 trillion watts — about twice the energy of all bombs used in World War II.
No immediate reports of casualties
A Dutch navy spokeswoman says that marines who flew to three islands hammered by Hurricane Irma have seen a lot of damage, but have no immediate reports of casualties.
The Category 5 storm made a direct hit Wednesday on the island where the Dutch territory of St. Maarten is located, though the scope of damage isn't yet clear. Some 100 Dutch marines flew to the islands on Monday to prepare for the hurricane.
Navy spokeswoman Karen Loos says that some troops were able to send images of destruction from St. Maarten and another island, St. Eustatius.
Loos says, "You do see there is a lot of damage. Trees, houses, roofs that are blown out. A lot of water, high water."
She says the extent of the damage elsewhere on the island is not yet clear.
The first of two Dutch naval vessels heading for the islands is expected to arrive at 8 p.m. local time in St. Maarten.
President Donald Trump says Hurricane Irma looks like "something that could be not good."
Ahead of a meeting with Congressional leaders Wednesday, Trump said the group had a lot to discuss, including what "seems to be record-breaking hurricane heading right toward Florida and Puerto Rico and other places."
Trump says "we'll see what happens." He adds: "it looks like it could be something that could be not good, believe me not good."
Hurricane Irma is the most powerful Atlantic Ocean hurricane in recorded history. It made its first landfall in the islands of the northeast Caribbean early Wednesday. Trump has declared emergencies in Florida, Puerto Rico and the U.S. Virgin Islands.
President Donald Trump's homeland security adviser says the government can handle Hurricane Irma relief because the life-saving phase for Hurricane Harvey is over and has entered a longer term phase focused on individuals.
Tom Bossert tells The Associated Press that the victims of Hurricane Harvey in Texas are not being forgotten as Irma hits the Virgin Islands and Puerto Rico and possibly Florida later this week. He says those in the path of the newest storm should heed evacuation orders.
For Harvey, he says the government is working on longer-term assistance, such as Small Business Administration loans, unemployment wages and reconstruction.