Schools are closed Wednesday across Puerto Rico as the island, still grappling with the devastation of 2017's Hurricane Maria, prepares for Tropical Storm Dorian.
The storm is expected to be near hurricane strength when it approaches Puerto Rico on Wednesday.
The storm's center is expected to pass over Puerto Rico, or near the western and central part of the island, before moving near the Dominican Republic on Thursday, with sustained winds perhaps just below the 74 mph threshold for a hurricane, according to the National Hurricane Center.
Hurricane or not, Dorian will batter Puerto Rico with heavy rain and strong winds, and it won't take much of either to cause trouble for the island's brittle infrastructure, CNN meteorologist Chad Myers said.
"There's already so much damage on the ground from (Maria) that this isn't going to take a lot to make a significant amount of damage, especially flooding," Myers said.
"Some of these power lines are not held up by very much -- 70 mph would bring them back down," he said.
Puerto Rico prepares
Gov. Wanda Vázquez Garced on Monday declared a state of emergency for the island, and urged people to prepare for the storm.
"For citizens who do not yet have safe roofs, we will have shelters ready," Vázquez said on Twitter.
About 360 shelters are available across the island for a capacity of 48,500 people, the government's official Twitter account said Monday. And about 70 hospitals were prepared to handle emergencies, officials said.
Puerto Ricans, still living with the devastation of Hurricane Maria in 2017, are on alert and preparing for what could be coming.
"Thankfully, I've been preparing since May," said Krystle Rivera, whose family has been stocking up on water, canned food and gas in anticipation of the hurricane season.
Lucy Beascochea told CNN she's a little nervous as she prepares for Dorian. Her home in Ponce, on the south side of the island, was destroyed by Maria, and it still hasn't been restored.
Beascochea said the roof leaks in the tiny apartment she lives in near her house, and her brother has been helping her tie down the roof and cover any holes in preparation for the next storm.
Ponce Mayor Maria "Mayita" Melendez estimates damages in her town alone had been as much as $1 billion from Maria, and there are still people with tarps over their homes, she told CNN.
The territory's department of education said public schools will be open only until 1 p.m. on Tuesday, as instructed by the governor, to allow for preparations of shelters and staff, the government said.
Puerto Rico and eastern parts of the Dominican Republic are under a tropical storm warning, and Puerto Rico is under a hurricane watch, the hurricane center said Tuesday evening.
A tropical storm warning means tropical storm conditions are expected within 36 hours, and a hurricane watch means that hurricane conditions are possible within 48 hours.
After passing Puerto Rico, Dorian is forecast to move near or over eastern Hispaniola on Thursday and move north, the hurricane center said.
By the end of the week, Dorian is expected to move toward the Bahamas and possibly into the southeastern parts of the United States as a Category 1 hurricane. Forecasts show Dorian approaching the Florida peninsula Saturday evening, but it's far too early to predict impacts there, CNN meteorologists said.
Where Dorian is now
On Tuesday evening, the storm's center was about 300 miles southeast of Ponce, Puerto Rico, with maximum sustained winds of 50 mph.
Dorian will dump heavy rain over some far-eastern Caribbean islands through Thursday. This includes Martinique, St. Lucia and St. Vincent, where rainfall generally will total up to 6 inches, with some isolated downpours of up to 10 inches, the hurricane center said.
From Wednesday to Thursday, Puerto Rico and the Dominican Republic could get 4 to 8 inches of rain, and the US Virgin Islands could receive 1 to 4 inches, according to the hurricane center.
Two-thirds of Puerto Rico is likely to receive tropical storm force winds, CNN meteorologist Brandon Miller said.
FEMA has positioned supplies in Puerto Rico and the US Virgin Islands ahead of the storm -- more than what was in place before hurricanes Irma and Maria in 2017 -- Acting Administrator Peter Gaynor said.
"Four Incident Management Assistance Teams are deploying today with another on standby," he said on Twitter.
In South Florida, more than 200 people from 30 fire departments prepared Monday to deploy into the storm's path, CNN affiliate WPLG reported.
"In this particular situation, we're going to be there before the storm hits, so we'll get a little familiarized with the area that we will be responsible for," Miami Fire Rescue Assistant Chief Scott Dean said. "We'll weather the storm where our base of operations will be located, and then as soon as the storm goes through and it's safe, our members will go into the streets and start operations and protect the search-and-rescue efforts."
This is peak hurricane season
Dorian is the fourth named storm of this Atlantic hurricane season, which generally peaks in the eight weeks surrounding September 10.
Two-thirds of all the storms produced in a typical season occur during this period.
That's because it's the time when conditions in the tropics become prime for storm development. By the end of August, waters in the tropics have warmed, and wind shear across the Atlantic begins to weaken.