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Hurricane Maria roared toward eastern Puerto Rico early Wednesday as the most powerful storm to threaten the region in almost 90 years.

Maria was a Category 5 hurricane — the strongest there is — when it killed one person and injured two others as it hit the Caribbean island of Guadeloupe on Monday night. "Widespread devastation" was also reported on Dominica.

At 5 a.m. ET Wednesday, the National Hurricane Center said Maria's eye was expected to make a landfall in Puerto Rico in "a couple of hours." Its maximum sustained winds were at 155 mph as it churned about 15 miles from Vieques, an island off Puerto Rico's eastern coast, and about 50 miles southeast of San Juan.

The center's bulletin added that tropical storm and hurricane conditions were already occurring over the Virgin Islands and spreading over Puerto Rico.

Less than an hour away from #Maria landfall. Will be strongest hurricane to hit #PuertoRico since a Cat 5 in 1928 pic.twitter.com/qdxz84oLlF — Bill Karins (@BillKarins) September 20, 2017

The storm weakened to Category 4 early Wednesday, and was expected to maintain that intensity until it makes landfall.

As far as destruction is concerned, the distinction between the two strongest categories is immaterial, said Orelon Sidney, a meteorologist for The Weather Channel, who said, "Whatever a 5 can do, a 4 can do."

"Locations may be uninhabitable for weeks or months," the National Hurricane Center warned.

The storm is expected to bring up to 16 inches of rain to the U.S. and British Virgin Islands and up to 25 inches to Puerto Rico, causing life-threatening flash floods and mudslides. The islands could also see several tornadoes throughout Wednesday.

Puerto Rico Gov. Ricardo Rosselló told reporters Tuesday that Maria "promises to be much more devastating" than was Hurricane Irma, which killed at least 70 people as it plowed through the Caribbean and the Southeastern United States earlier this month.

"If you are in a flood zone, your life is in danger," Rosselló said. "If you are in a wooden house, your life is in danger."

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Héctor Pesquera, Puerto Rico's commissioner of public safety, was even more blunt.

"You have to evacuate — otherwise, you are going to die," he said, according to Telemundo, NBC's Spanish-language network. "I do not know how to make this any clearer."

Early Wednesday, Rosselló tweeted that more than 11,000 people and nearly 600 pets were waiting out Maria in 500 shelters.

Police trying to secure doors inside the Roberto Clemente shelter but #HurricaneMaria winds are too strong. #PuertoRico pic.twitter.com/oU88mIKj5C — Gadi Schwartz (@GadiNBC) September 20, 2017

Some who chose to flee Puerto Rico and the U.S. Virgin Islands ahead of Maria arrived at airports in Florida Tuesday, APTN reported.

"I live on St. John and we were there for Irma when Irma came through and she just basically devastated the island," said Patrick Coffey, a resident of the U.S. Virgin Islands. "A lot of people lost everything and then it was just time for us to get off, we didn't want to stay for Maria."

Louis Santos, who flew to Florida from Puerto Rico, said he still remembers dealing with the devastating effects of Hurricane Georges that hit the island in 1998.

"This time it's going to be worse," Santos said. "It's going to be a Category 5. That, back then, was a Category 3."

Core of potentially catastrophic category 5 Hurricane #Maria expected to reach southeastern Puerto Rico this morning https://t.co/tW4KeGdBFb pic.twitter.com/8XTrWJIPdO — NHC Atlantic Ops (@NHC_Atlantic) September 20, 2017

President Donald Trump has declared states of emergency in both territories, and the Coast Guard has moved all its ships, aircraft and personnel out of harm's way so they can quickly launch rescue missions once the storm passes, officials said.

Hurricane warnings also went up in the Dominican Republic from Cabo Engano to Puerto Plata. Maria was expected to skirt just north of the Dominican Republic on Wednesday night and Thursday, according to forecasters.

The last time the region was threatened by a storm this powerful was in 1928, when the Okeechobee Hurricane roared through the Virgin Islands and slammed Puerto Rico. It killed more than 300 people there and left a trail of destruction from one end of the island to the other before heading on to Florida.

In the end, it wound up being one of the deadliest hurricanes on record to hit North America, killing more than 4,000 people — most of them poor black residents who lived near Lake Okeechobee in South Florida and whose bodies were buried in mass graves.

But back then, Puerto Rico had a population of less than 1.5 million and was largely rural. Today, the population is nearly 3.5 million. And it's still feeling the effects of Irma, which at its worst point cut off power to more than 1 million people.

With several days to prepare, many Puerto Ricans stocked up on supplies, boarded up their homes and headed once again for shelters and higher ground.

Morales, 48, the mother of two children, said she would ride out the storm with her parents and brother at a home in Rio Piedras.

"Everybody's tense. The streets are a little crazy now," she said. "The streetlights aren't working. Gas stations — the ones that do have gas, the lines — are incredible. People are like a little bit crazy, panicked."

Cat 5 #Maria has sustained winds of 165 MPH and a staggeringly low pressure of

26.87". The eye is forecast to cross #PuertoRico today. pic.twitter.com/r7ueZ7Vhk6 — NASA SPoRT (@NASA_SPoRT) September 20, 2017

Maria roared through Dominica and Guadeloupe overnight. One person was killed by a falling tree on Guadeloupe and two other people were still missing after a boat disappeared off the coast, authorities said.

In Dominica, the 72,000 or so residents were digging out after the storm.

"Initial reports are of widespread devastation," Prime Minister Roosevelt Skerrit reported on his Facebook page. "So far we have lost all what money can buy and replace."

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Skerrit reported Monday night that he'd had to be rescued from his own home, the roof of which was blown off.

"Dominica had very little time to prepare for this monster... the strongest storm of their lifetimes," said NBC News meteorologist Bill Karins, who highlighted that Maria was one of the fastest-growing hurricanes ever recorded.

The French island of Martinique, which at one point appeared poised to take a direct hit from Maria, also sustained heavy damage, authorities said.

It's only the second time in recorded history that two Category 5 hurricanes have made landfall in a hurricane season, Karins said. The last time that happened in the Atlantic basin was in 2007, when Dean and Felix killed 174 people in Mexico and Central America. They were so destructive that both of their names were retired.