The core of Maria, a major hurricane, is forecast to pass just east of the Turks and Caicos and southeastern Bahamas early Friday.
The Category 3 storm has sustained winds of 125 mph, the US National Hurricane Center said.
In just 24 hours, Maria dumped almost 40 inches of rain on parts of Puerto Rico, where millions of residents won't have power for months. Most of the island saw more than a foot of precipitation as Maria turned streets into raging rivers.
The storm brought down trees and poured up to 6 inches of rain on the Dominican Republic as the eyewall passed to the east.
Many Puerto Ricans spent Thursday cleaning up. A man in the La Perla area of San Juan told CNN he still had his faith. "It's incredible ... but I believe in God, and we can do anything with the help of God," Roberto Caballero said.
CNN teams in San Juan saw that some shops were open. All had long lines.
Maria has brought misery to many Caribbean Islands and death to Dominica, where at least 15 people were killed when the storm passed earlier this week, according to Prime Minister Roosevelt Skerrit.
Here's the latest on Maria's destruction, and what's next.
Dominican Republic gets thrashed
Although Maria is drifting away from the Dominican Republic, parts of the country are still seeing hurricane conditions, the National Hurricane Center said.
"A dangerous storm surge accompanied by large and destructive waves will raise water levels by as much as 4 to 6 feet" in parts of the Dominican Republic -- where rivers were still swollen from Hurricane Irma, forecasters said. Haiti, on the western part of the island, could see a storm surge of up to 3 feet.
Maria will likely strengthen as it moves across warm water, endangering low-lying islands with enormous storm surges. And the Turks and Caicos could see as much as 20 inches of rainfall, the hurricane center said.
Maria could affect the US East Coast by early next week
with high surf, dangerous rip currents and windy conditions. Depending on its path, the system could also bring rain from the mid-Atlantic to Massachusetts, CNN meteorologist Michael Guy said.
Puerto Rico: Power system 'basically ... destroyed'
Puerto Ricans might not get power back for four to six months, said Ricardo Ramos, the CEO of Puerto Rico Electric Power Authority.
"The system has been basically destroyed," Ramos told CNN. He said hospitals and water systems will get priority power restoration.
The island's largest airport, the Luis Muñoz Marín International Airport, will be open to commercial traffic Friday, according to Aerostar Puerto Rico, which manages the airport near San Juan.
Emergency generators will power the limited operations, and there will be no air conditioning, the operator said.
President Donald Trump told reporters that he will visit Puerto Rico, a US commonwealth, but did not detail when.
"Puerto Rico was absolutely obliterated," Trump said. "We'll work with the governor and the people of Puerto Rico."
Gov. Ricardo Rosselló said Maria is the "most devastating storm to hit the island this century, if not in modern history."
Puerto Rico has been through a long recession and is deeply in debt.
Before the storm hit, the state-owned power grid was "a little bit old, mishandled and weak," the governor said.
Retired Army veteran Manuel Torres called Maria's devastation the worst he'd ever seen. His mother's house in La Perla, an oceanfront community in old San Juan, was destroyed.
Emerging after the storm had passed, Torres found the three-story home reduced to two stories.
Angela Magaña, a UFC fighter who lives in the area, said neighbors were helping each other.
"We need cleanup, water, food, and generators," she told CNN. "There are a lot of old people here who are going without necessities. We need to rebuild and restructure, and we need prayers. Any kind of help we can get because it's a mess right now."
Dozens of families were rescued from flooding Thursday in Levittown, near the capital city of San Juan, a spokeswoman for the Puerto Rican governor tweeted. The Puerto Rican National Guard was still searching for others in need of rescue, she said.
Cassidy Spooner, a tourist from Jacksonville, Florida, came upon animals as she was checking out the damage in Luquillo on Thursday.
"The dog was looking for food. I saw her find raw bacon in the street and eat it," she said. Spooner told CNN she saw kittens and cats near a house nearby that appeared to have cat food, but the felines looked skinny and scared.
Neighbors were trying to take care of the animals, she said.
Army Reserve Brig. Gen Dustin Shultz told "CNN Tonight with Don Lemon" there are 4,500 reserve soldiers on Puerto Rico to assist the National Guard.
Dominica: 'The need is great'
Prime Minister Skerrit said Dominica was almost completely devastated.
"First of all, every village in Dominica, every street in Dominica ... is affected by the hurricane," he told ABS TV/Radio, based in Antigua and Barbuda. "We have no running water, no electricity, no power, we have very limited communication services." Skerrit's own home was demolished in the storm.
There is desperate need for food, water and medical supplies on the island of 73,000 residents, officials said.
"The need is great," said Philmore Mullin, head of Antigua and Barbuda's National Office of Disaster Services. "We know of casualties, but not in detail. We've heard of many missing, but we just don't know much at the moment."
Skerrit is "homeless" and "bunking up in an area called St. Aroment," government spokesman Charles Jong said.
A flight Wednesday over Dominica showed thousands of trees had been snapped and were strewn across the landscape, leaving the island stripped of vegetation.
CNN also saw evidence of dozens of mudslides, although not in population centers. The usually blue-green sea in many places had turned a muddy brown.
US Virgin Islands: 24-hour curfew in place
Maria also annihilated homes on the US Virgin Islands. On Thursday, Gov. Kenneth E. Mapp announced a 24-hour curfew, effective immediately, on the four main US Virgin Islands -- St. Croix, St. Thomas, St. John and Water Island.
"Your presence on the roads during the curfew hours will only hamper clean-up efforts and could delay the distribution of critically needed supplies," Mapp said.
One of the hardest hit islands was St. Croix. Maria didn't just obliterate homes, it knocked out vital communication lines, resident Murillo Melo said.
"Here on the island and on the mainland, people are trying to get in contact with friends and relatives," he said. "People are desperate to get some news from their friends and relatives."
Trump declared the US Virgin Islands a major disaster area and ordered federal aid to supplement recovery efforts.