Tropical Storm Ernesto dropped torrential rain on eastern Puerto Rico early Wednesday and left hundreds of thousands of people without power in the U.S. territory as it threatened to strengthen into a major hurricane en route to Bermuda.

A hurricane watch remained in effect for the British Virgin Islands as Ernesto began moving over open waters.

The storm was located about 85 miles (135 kilometers) north-northwest of San Juan, Puerto Rico. It had maximum sustained winds of 70 mph (110 kph) and was moving northwest at 16 mph (26 kph).

“While it is possible Ernesto is already a hurricane, radar data does not yet support an upgrade,” the National Hurricane Center in Miami said.

Ernesto is expected to become a hurricane later Wednesday morning.

A tropical storm warning was in effect for Puerto Rico, Vieques, Culebra and the U.S. and British Virgin Islands.

Ernesto is forecast to move through open waters for the rest of the week and make its closest approach to Bermuda on Saturday. It is expected to become a major Category 3 storm in upcoming days, with forecasters warning of heavy swells along the U.S. East Coast as Ernesto moves north-northwest in the Atlantic.

Between 4 to 6 inches of rain is expected in the U.S. and British Virgin Islands, and between 6 to 8 inches in Puerto Rico, with up to 10 inches in isolated areas.

The government of the U.S. Virgin Islands reported an island-wide blackout in St. Croix, while in Puerto Rico, more than 300,000 customers were without power.

Late Tuesday, the U.S. Federal Emergency Management Agency had warned people in both U.S. territories to prepare for “extended power outages.”

Luma Energy, the company that operates transmission and distribution of power in Puerto Rico, said early Wednesday that its priority was to restore power to hospitals, the island’s water and sewer company and other essential services.

Puerto Rico’s power grid was razed by Hurricane Maria in September 2017 as a Category 4 storm, and it remains frail as crews continue to rebuild the system.

Not everyone can afford generators on the island of 3.2 million people with a more than 40% poverty rate.

“People already prepared themselves with candles,” said Lucía Rodríguez, a 31-year-old street vendor.

Puerto Rico Gov. Pedro Pierluisi announced late Tuesday that U.S. President Joe Biden had approved his request to use emergency FEMA funds as a result of the tropical storm.

Ernesto is the fifth named storm of this year’s Atlantic hurricane season.

The National Oceanic and Atmospheric Administration has predicted an above-average Atlantic hurricane season this year because of record warm ocean temperatures. It forecast 17 to 25 named storms, with four to seven major hurricanes of Category 3 or higher.

(AP)