Tropical Storm Dorian strengthened to a hurricane Wednesday afternoon as it threatened the Virgin Islands and Puerto Rico, with forecasters predicting it could become a Category 3 hurricane by the time it hits Florida over the weekend.

Dorian became a hurricane near the island of St. Thomas in the U.S. Virgin Islands, according to the National Hurricane Center. There were multiple observations of hurricane-force winds in St. Thomas, according to the hurricane center.

FOLLOW THE STORM | Channel 3 Hurricane Tracker

The storm was expected to move near or over the U.S. and British Virgin Islands Wednesday afternoon and then move over the Atlantic Ocean east of the southeastern Bahamas, the hurricane center said.

As of Wednesday afternoon, hurricane warnings were in effect for the U.S. Virgin Islands, the British Virgin Islands and Puerto Rico’s island municipalities of Vieques and Culebra. A hurricane watch and tropical storm warning were in effect for Puerto Rico.

The hurricane center said the storm’s maximum sustained winds had increased to 75 mph with higher gusts, and forecast that Dorian could strengthen to a Category 3 hurricane as it nears Florida this weekend and early next week.

Rainfall from the storm could cause 'life-threatening flash floods," according to the hurricane center.

The storm was tracking more north than most forecasts had predicted and could pass Puerto Rico to its east, drastically increasing the odds of a hurricane landfall in the southeast U.S., wrote Brian McNoldy, a senior research associate at University of Miami's Rosenstiel School of Marine and Atmospheric Science.

But the storm could still prove a major test of Puerto Rico’s electrical grid two years after Hurricane Maria wiped out power on the entire island and thousands died in the aftermath of the storm. In some areas, power was only fully restored a year later.

The island was already seeing heavy rain Wednesday as conditions worsened. The worst was expected from Wednesday afternoon to early Thursday before the storm pulls away. The eastern part of the island and the Virgin Islands were expected to get 4 to 6 inches of rain, with isolated areas seeing as much as 10 inches.

Late Tuesday, President Donald Trump approved a state of emergency declaration for Puerto Rico, allowing federal authorities to coordinate aid efforts.

But on Wednesday morning, the president had this message for the U.S. territory: “Puerto Rico is one of the most corrupt places on earth. Their political system is broken and their politicians are either Incompetent or Corrupt,” he tweeted. “Congress approved Billions of Dollars last time, more than anyplace else has ever gotten, and it is sent to Crooked Pols. No good!”

Trump has repeated a false claim that Congress sent $92 billion of aid money to Puerto Rico. Congress has allocated $42.5 billion to disaster relief for Puerto Rico, according to federal data, but the island had received less than $14 billion through May.

Trump then said he was “the best thing that’s ever happened to Puerto Rico!”

Earlier Wednesday, Trump said they were tracking Dorian “as it heads, as usual, to Puerto Rico.”

Trump then defended the Federal Emergency Management Agency, which was widely criticized in the aftermath of Hurricane Maria in September 2017, and targeted a regular critic of his, San Juan Mayor Carmen Yulín Cruz.

“FEMA and all others are ready, and will do a great job. When they do, let them know it, and give them a big Thank You — Not like last time,” Trump tweeted. “That includes from the incompetent Mayor of San Juan!”

In San Juan, volunteers went door to door to make sure residents were prepared. Many homes on the island are still covered by blue tarps from Hurricane Maria.

Jorge Ortiz, 50, a construction worker who had the second floor of his house ripped off in that storm and just finished rebuilding three months ago, without local or federal assistance, told The Associated Press that he was worried he would "lose it again."

Cruz said the island was prepared, but added: “We’re scared. We know what may be coming."