SAN JUAN, Puerto Rico (CNN) - Hurricane Maria has made landfall as of 6:20 a.m. Wednesday morning, bringing 155 mph winds to the U.S. territory.
Thousands of Puerto Ricans heeded the calls of government officials and have taken refuge in shelters as the Caribbean island braces for Hurricane Maria's direct hit early Wednesday.
"As of 2:30 a.m. we count 10,059 refugees and 189 pets (in shelters)," a tweet from the island's governor, Ricardo Rosselló says. On Tuesday, he called Maria an "unprecedented" atmospheric system.
Maria is currently a Category 4 hurricane - with 155 mph wind speeds.
Conditions are expected to worsen between 8 a.m. and 9 a.m. Wednesday, when the storm's eye wall -- and the strongest winds that it will bring with it -- hits the eastern coast of the island.
As millions of the island's residents hunkered down in their homes, others in the most vulnerable areas -- the low-lying, flood-prone areas -- have been evacuated.
The Puerto Rico Convention Center in San Juan -- which is still housing Hurricane Irma evacuees from other Caribbean islands -- is preparing to accept thousands of residents as the worst of the storm is felt.
Potentially 'strongest ever' storm
The storm is likely to be a record-breaking event, CNN meteorologist Derek Van Dam says.
"This could potentially be the strongest hurricane to ever reach the shores of Puerto Rico.
"A lot of people remember or have heard of the storms that hit in 1928 and 1930 -- well guess what? This could pale those in comparison. The central pressure of this storm is at 908 millibars -- that is the tenth lowest pressure recorded in Atlantic basin hurricanes.
"It will go down in the record books."
Storm surges of 6 to 9 feet are expected.
"Hurricane Maria is really scraping the upper echelon of what's possible with hurricanes, (with) 175 mph sustained winds right around the center of the storm," Van Dam said from the island's capital.
The island's mountainous terrain will act like a barrier and squeeze out a lot of the moisture, he says, producing up to 2 feet of rain in some areas, which could lead to flash flooding -- which Rosselló stressed was the number one cause of death following a storm of this nature.
Local politicians warned of the storm's impact, but also stressed the importance of the islanders' spirit.
"We are going to be hit hard," San Juan Mayor Carmen Yulin Cruz told CNN. "But we are blessed that we have what it takes to move and push on.
"We will make it, I bet you. I have no doubt, we're going to make it."
Most on the island have heeded the increasingly urgent warnings from the island's government to stock up and stay indoors.
A CNN team shopping for supplies in San Juan earlier Tuesday said the store they went to was busy, but orderly.
A sign on the shelves asked customers to limit buying to two cases of water, but the store had already run dry by the time the team arrived. The store did still have food and other supplies.
At a gas station across the street from the store, the attendant said the station ran out of regular gas in the early hours of Tuesday morning and had since run out of premium gas.
Shoppers looking for essentials such as ice needed to wait for hours to buy the commodity, which will be used to keep perishables cool in power outages.
Rosselló told CNN's "Anderson Cooper AC360˚" that the government has been "organizing" ahead of the storm.
"We can get people out of harms way, flooding regions, and make their way to safe shelters," he said.
"What we're doing is making sure people can pass through, they can weather the storm. It's not going to be comfortable, but they're going to be safe. This is our key objective.
"We understand infrastructure is going to be devastated. We're going to have rebuild. But lives are not replaceable but infrastructure is."
Some tourists found themselves stranded on the island as flights -- already overbooked and increasingly expensive -- dried up.
Heather Farrell, a visitor to the island, is on her honeymoon with her husband Luke. They were married on September 9. She says that they had tried to cut their trip short when it became apparent they were in Maria's firing line.
"We did try to get off, as early as Saturday but all flights were either booked or canceled. We actually are on the ocean -- our room faces the ocean. It's pretty windy but there is no rain. We'll stay inside for now."
She said hotel staff had asked that all guests staying at the hotel come downstairs early Wednesday morning to a safe room that they have set up for them.
"I would rather be home than here, but I guess we're making the best of it," she said.
Nick Bailey, Brandon Edwards and John Michael Berndt -- three friends from northern California -- chose this week to vacation on the island. They were aware of the existence of Hurricane Maria, but when they left California it was only a tropical depression.
Now the friends brace themselves to endure the Category 5 tempest.
"We were anxious this morning but our hostel is taking good care of us. We tried to take flights out last minute but that didn't work so we're going to ride through the storm," Berndt said.
The hostel where they're staying has boarded all the windows and created a concrete hurricane barrier, helping the three men feel safe.
"This is a good area apparently," Bailey said. "It's close to hospitals and emergency centers."
In addition, their rooms have been relocated to ones that are deeper inside the hostel without any windows.
Man killed by falling tree in Guadeloupe
Two other people are missing after a boat sank off the coast of La Désirade, a smaller island near the mainland of Guadeloupe. The government said about 80,000 people, or 40% of the households on the island, are without power.
The storm also caused "widespread devastation" in Dominica, Prime Minister Roosevelt Skerrit said Tuesday.
The hurricane shredded the prime minister's house overnight and left much of the island -- population 73,000 -- in ruins.
In just 30 hours, Maria's intensity exploded from 65 mph on Sunday to 160 mph by Monday night, the National Hurricane Center said.
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