A woman stares to the sea in front the iconic El Morro Fortress in Old San Juan on Tuesday ahead of Hurricane Maria’s expected arrival. (DENNIS M. RIVERA PICHARDO/For The Washington Post)

Residents of Puerto Rico were bracing for a possible direct hit from Hurricane Maria early Wednesday morning, the latest powerful storm to barrel across the Atlantic Ocean while menacing the islands of the Caribbean and threatening the United States.

Residents here rushed to get fuel and scrambled to book last-minute flights out of harm's way in advance of Maria, which had strengthened to a massive Category 5 hurricane with potentially catastrophic winds. The storm caused widespread damage in the island nation of Dominica this week and is blamed for at least one death on the French island of Guadeloupe.

Forecasters say the hurricane is on track to pummel the island of St. Croix in the U.S. Virgin Islands, followed by an expected path through Puerto Rico, home to 3.5 million U.S. citizens. The island has not seen a hurricane make landfall since Georges in 1998, and it narrowly missed taking the brunt of Hurricane Irma recently when that storm passed to the north on its way to Florida.

Puerto Rico Gov. Ricardo Rosselló called Maria potentially historic and warned residents to take it seriously. Authorities preemptively dredged canals to funnel away floodwater, set up 500 emergency shelters and urged residents to stock up on food and water.

"This is an unprecedented atmospheric system," Rosselló said in a statement. "It's time to act and look for a safe place if you live in flood-prone areas or in wooden or vulnerable structures."

The National Weather Service on Tuesday called Maria "potentially catastrophic," with rainfall that could total between 12 and 18 inches and, in some places, as much as 25. It warned of the possibility of "structural damage to sturdy buildings, some with complete roof and wall failures." Some locations, it said, could be "uninhabitable for weeks or months."

Empty shelves at local supermarket in San Juan on Tuesday as Puerto Rico readies for the arrival of Hurricane Maria. (DENNIS M. RIVERA PICHARDO/For The Washington Post)

The grave warnings echo those delivered by authorities in Florida, Texas and other areas ahead of devastating hurricanes in recent weeks that have claimed dozens of lives in the United States and the Caribbean.

The 2017 hurricane season already has featured four storms registering at Category 4 or higher, putting it on par with some of the most intense seasons in U.S. history — with more than two months remaining.

Just over a week ago, Florida and parts of the Virgin Islands were strafed by Irma, a massive storm that struck the Florida Keys as a Category 4. Days before that, Hurricane Harvey swept across the Gulf of Mexico to deliver record floodwater to Houston as the storm stagnated over Texas.

As Maria swirls westward, the remnant of another hurricane is threatening parts of the East Coast, from Delaware to eastern Massachusetts.

What is left of Hurricane Jose is forecast to weaken, and its center is expected to pass well offshore. But Jose could still bring heavy winds and moderate flooding to coastal beach areas.

If Maria's impact on the tiny island nation of Dominica is any indication, the dire warnings are warranted.

In a breathless series of Facebook posts Monday night, Prime Minister Roosevelt Skerrit described furious winds that tore off the roof of his official residence. "My roof is gone. I am at the complete mercy of the hurricane. House is flooding," he wrote at about 9:20 p.m. Monday.

He was quickly rescued, but his posting a few hours later expressed no great relief.

"So far we have lost all what money can buy and replace," he wrote. "My greatest fear for the morning is that we will wake to news of serious physical injury and possible deaths as a result of likely landslides triggered by persistent rains."

Dominica, with a population of 72,000, is a country about the geographic size of greater New York City. A sovereign nation that gained its independence from Great Britain in 1978, it bills itself as the "Nature Island" of the Caribbean for its lush volcanic mountains and tropical rain forests.

On Tuesday morning, officials on the French island of Guadeloupe said that 80,000 homes there were without power and that there was an increased risk of flooding and landslides.

Images from the islands showed felled trees strewn about the roads and neighborhoods submerged in water. There were reports that Maria had caused at least one fatality there

In Puerto Rico, preparations have been complicated because it is still recovering from Irma, which skirted to the north but left at least one dead and large areas of the island without power.

José Valderrama, 78, a resident of a poor neighborhood in San Juan, waits to evacuate his house with his daughter and granddaughter. (DENNIS M. RIVERA PICHARDO/For The Washington Post)

Residents of San Juan, the capital city, appeared to be heeding officials' warnings to get ready, with many preparing since the weekend with a growing sense of unease and resignation.

At a gas station in Barrio Obrero, Manuel Rivera sat huddled in the back of a red Jeep on Tuesday afternoon surrounded by water jugs full of gas.

His friends filled them one by one to ensure they would have enough fuel for the generator at their home. They had electricity for now, but they expected it could be gone by nightfall.

"The power leaves when it wants to," Rivera said. After Irma, his home was without power for about a week.

Grocery and convenience stores had run out of water and ice. Neighborhoods were quiet, save for a few cars on the roads and the sound of people banging boards across their windows.

"Of course I'm nervous, but I feel prepared," said Wilfredo Torres, 36, one of the men installing corrugated steel storm windows outside the post office in the Miramar neighborhood. "There's another storm coming. Maria is coming, and there's nothing you can do. You have to prepare and then wait and see."

Workers cover the windows of a U.S. Post Office with storm shutters in San Juan on Tuesday. (DENNIS M. RIVERA PICHARDO/For The Washington Post)

A family from Bayamon braved the winds for a brief walk along Avenida Munoz Rivera on the waterfront, bored after being cooped up in their house all day setting up for the hurricane.

"Everyone is calm but tense," said Jorge Velez, out with his wife, Arleen Santini, and their son, Ricardo, 6. "I've seen David, Hugo and Ortensia. But what Maria brings is double the force."

With that, drops began to fall from the sky, and the strengthening winds tilted the palm trees along the waterfront.

Velez and his family rushed to their white SUV, dodging the rain and heading back home for the night.

Fear also rippled across Vieques, a tiny island off Puerto Rico's east coast that is home to about 9,500 residents, many of whom live below the poverty level and are accustomed to dealing with some measure of hardship. Many there evacuated during Irma and opted to stay put for Maria but are now having second thoughts.

"I regret not leaving," said Marie Rivera, 56, whose parents live on Puerto Rico's main island. "I'm not sure when I will be able to see my family again. I'm starting to get a little anxious now."

Irma left many here without power for days. In an unfortunate twist, some residents of Vieques had stocked up on critical supplies in advance of Irma only to donate what they had left to harder-hit areas such as Tortola and St. Thomas. Residents rushed to restock before deliveries to the island stopped and the power flickered off yet again.

President Trump on Sunday declared emergencies in the U.S. Virgin Islands and Puerto Rico in advance of Maria.

The Federal Emergency Management Agency has embedded workers across the U.S. territories in the Caribbean, including in parts of the U.S. Virgin Islands affected by Irma, to ensure residents have food and water before the storm.

The U.S. military is expected to assist Puerto Ricans after the storm hits, but is mostly steering clear beforehand to avoid being caught up in it and unable to help, military officials said. 

Adm. Paul Zukunft, the commandant of the Coast Guard, said in an interview late Tuesday that his service has staged rescue helicopters at the Navy base at Guantanamo Bay, Cuba, far enough out of the way to avoid the worst of the storm but close enough to respond quickly afterward. Puerto Rico's island geography may require a lot of the assistance to come from ships, he said. 

"We have moved all of our ships out of San Juan," Zukunft said. "They have not seen winds like this ever, so I think the devastation is going to be significant. We're working very closely with FEMA, and the Navy has a significant flotilla of ships in this area. We've got aircraft that will come in behind it."

Recovery efforts in Puerto Rico could be hampered by long-standing financial problems that led the territorial government to file for a form of bankruptcy in May.

More than 500 residents of San Juan are taking refuge at Roberto Clemente Coliseum, the biggest shelter on the island. (DENNIS M. RIVERA PICHARDO/For The Washington Post)

Schmidt and Cassady reported from San Juan and Somashekhar reported from Washington. Amy Gordon in Vieques, Puerto Rico; Anthony Faiola in Miami; Rachelle Krygier in Caracas, Venezuela; and Jason Samenow, Dan Lamothe and Amy B Wang in Washington contributed to this report.