Dorian strengthened to a Category 1 hurricane Wednesday as it lashed the U.S. and British Virgin Islands with heavy rain and took aim at Puerto Rico.
After the storm passes through Puerto Rico, it will move north, potentially becoming a major Category 3 hurricane when it reaches Florida over the holiday weekend.
Dorian won't make landfall in Puerto Rico but will pass to the east of the island Wednesday afternoon and evening, bringing up to 75 mph winds, 10 inches of rain and possibly flash flooding.
The Puerto Rican government said it is fully prepared for the storm's impact. Gov. Wanda Vazquez said Monday night that the government is 90% ready to deal with any possible damage Dorian might cause.
Meanwhile, many in Puerto Rico are still reeling from the devastation of 2017's Hurricane Maria, including tens of thousands of residents living under blue tarp roofs.
More than 7,400 generators and three mega generators are already on the island, according to the governor, and at least 360 shelters will open, accommodating up to 48,500 people.
President Donald Trump has approved an emergency declaration, which will provide federal assistance in Puerto Rico.
"The communication with all [of the president's] aides has been extraordinary," Vazquez said Monday.
A new Federal Emergency Management Agency (FEMA) representative is on the island assisting in response coordination.
The response "will be on top of a complex recovery effort," a FEMA spokesperson said. "Even a smaller and less severe storm could have significant impact."
Once Dorian passes through the Caribbean, it's forecast to steer toward Florida over the Labor Day weekend.
Dorian could make landfall on the East Coast of Florida on Monday morning as a major Category 3 hurricane with winds up to 115 mph. The Southeast coastline from Miami to Charleston could see impacts.
Jacksonville, Florida, will activate its emergency operations center full-time as Dorian nears, Mayor Lenny Curry said at a news conference Wednesday.
Curry said it's too early to make any decisions about possible evacuations, but residents should make sure they know their evacuation zone.
The storm is also impacting Labor Day travelers. Some airlines have issued travel waivers, and Royal Caribbean is closing its private island in the Bahamas for a week and altering some of its cruise ship itineraries to avoid Dorian.
As the Atlantic hurricane season nears Sept. 10 -- its peak -- Dorian isn't the only storm on the move. Newly-formed Tropical Storm Erin is expected to bring rough surf to the East Coast beaches from the Carolinas to New England this Labor Day weekend.
Otherwise, it is not expected to directly impact the East Coast.