Hurricane Ernesto is heading for the Caribbean island of Bermuda, having crossed Puerto Rico where it left more than half of homes and businesses without power, APA reports citing ABC.
Puerto Rico's main power supplier Luma Energy was reporting that some 410,000 customers did not have access to electricity by around midday Thursday, according to Reuters news agency.
Ernesto, which grew into a category-one hurricane on Wednesday, is continuing to strengthen with gusts of up to 90mph (150km/h) ahead of its expected landfall in Bermuda on Friday.
Forecasters predict it could become a major hurricane in the next 48 hours, and have warned of flash flooding, strong winds and dangerous ocean swells.
Ernesto is expected to continue to strengthen as it heads towards Bermuda - a British territory made up of 181 islands in the Atlantic ocean.
By Saturday it is expected to become a "large hurricane", according to US weather forecasters. It will then move back out to sea as it travels up the US East Coast. Next week it could brush Atlantic Canada.
Forecasters have previously warned of the role of climate change in making storms like this one more intense.
Ernesto swept past Puerto Rico overnight, with up to 10in (25cm) of rain expected in some places, the US National Hurricane Center (NHC) said.
"Preparations to protect life and property should be rushed to completion," the agency warned in a bulletin on Thursday evening.
Juan Saca, Luma's president and chief executive, said more than 1,500 employees were working in the field to "re-establish service" and switch the electricity back on.
"We have to evaluate what needs to be done to be able to resolve it," he told Reuters.
Puerto Rico's power grid has been wiped out before by hurricanes. In 2022, when Hurricane Fiona hit the island, around 80% of homes and businesses were cut off for almost a month.
Ernesto is the fifth named Atlantic storm to occur this season.
Hurricane Beryl 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 leaving millions without electricity.
Earlier this year, US weather agency Noaa warned that the North Atlantic could get as many as seven major hurricanes of category-three strength or over this year, which would be more than double the usual number.
While there is no evidence climate change is producing more hurricanes, it is making the most powerful ones more likely, and bringing heavier rainfall.
