Hurricane Ernesto on Thursday barreled toward Bermuda where it threatened powerful winds, a dangerous storm surge and heavy rains over the weekend after leaving hundreds of thousands of Puerto Ricans without power in its wake.

Now a Category 1 hurricane, Ernesto is forecast to strengthen into a much more powerful hurricane before it reaches Bermuda late on Friday, a British island territory far out in the Atlantic, the National Hurricane Center (NHC) said.

At 5 p.m. ET (2100 GMT) on Thursday it was located 495 miles (795 km) southwest of Bermuda as it headed north, packing winds of 85 miles per hour (140 kph).

“Strengthening is forecast during the next day or so, and Ernesto could be near major hurricane strength by Friday,” the NHC said. A major hurricane is a Category 3, 4 or 5 on the five-step Saffir-Simpson Hurricane Wind Scale and is capable of causing devastating or even catastrophic damage.

“Preparations to protect life and property should be rushed to completion,” the NHC warned in its latest advisory.

By Saturday, Ernesto will have become what the NHC describes as a “large hurricane,” as its center passes near or directly over the islands, where it will produce up to 15 inches (38 cm) of rain, prolonged strong winds, flash flooding and a dangerous storm surge.

Only 11 storms have made direct landfall on Bermuda, an archipelago of 181 islands with a population of 64,000, since records began in 1851.

Hurricanes Gonzalo in 2014 and Fabian in 2003 were the most destructive storms to hit Bermuda in recent memory, causing hundreds of millions of dollars in damage and leaving most of the islands without electricity. Fabian killed 4 people, the first storm to cause deaths on the islands since 1926.

Ernesto became a hurricane on Wednesday after leaving Puerto Rico as a tropical storm, where it battered the island with heavy rainfall. Images and video footage from the island showed flood waters covering roadways, downed powerlines and destroyed homes and vehicles.

As of midday on Thursday, some 410,000 homes and businesses – about a quarter of all customers on the U.S. territory – remained without electricity, according to LUMA Energy, the Caribbean island’s main power supplier.

Vanessa Toro, a San Juan resident who lost electricity early on Wednesday morning, said she was frustrated that she was still without power even though the storm itself had little impact on her area.

“If the event had been of a large magnitude, one understands the situation a little more, but this storm was not catastrophic,” she said. “Then LUMA says it is prepared to deal with these situations, but we are without power 29 hours after the storm.”

LUMA Chief Executive Juan Saca said in a radio interview on Thursday morning that he expected power to be restored to many customers later on Thursday.

Puerto Rico’s power grid is notoriously fragile. In 2022, Hurricane Fiona knocked out power for about 80% of the island’s homes and businesses for as long as a month. Five years earlier, Hurricanes Irma and Maria destroyed the island’s power grid and caused outages in some areas that lasted nearly a year.

Ernesto was expected to stay well west of the U.S. East Coast as it traveled north over the ocean. However, the storm was forecast to produce life-threatening surf and rip currents across the region, the center said.

Ernesto is the fifth named Atlantic storm of what is expected to be an intense hurricane season. Slow-moving Debby hit Florida’s Gulf Coast as a Category 1 hurricane just last week before soaking some parts of the Carolinas with up to 2 feet (60 cm) of rain.

Hurricane Beryl, the first of the season, was the earliest Category 5 storm on record in the Atlantic when it swept through the Caribbean and the Texas Gulf Coast last month, killing dozens of people and costing an estimated $6 billion in damages.