Ernesto was about 280km/h northwest of the Puerto Rican capital of San Juan as it crawled to the northwest, packing winds of about 120 km/h, the US National Hurricane Center said in a Wednesday advisory.
"The official forecast still reflects the possibility of Ernesto becoming a major hurricane in about 48 hours," the centre said.
A storm is considered a hurricane when its sustained winds reach 119 km/h.
A major hurricane - a category three or higher - has a sustained wind speed of at least 179km/h.
Ernesto - the fifth named Atlantic storm of the season - should approach the UK island territory of Bermuda, about 1100km east of North Carolina, by Saturday, with rainfall beginning as early as Thursday, the NHC said.
11 am EDT Wednesday, Aug. 14 Key Messages for Hurricane — National Hurricane Center (@NHC_Atlantic) #Ernesto.Risk of life-threatening surf and rip currents is expected to increase along the U.S. East coast beaches this weekend.https://t.co/mxowVoRB8e pic.twitter.com/cGBJA7WcdXAugust 14, 2024
More than 500,000 homes and businesses were without power early on Wednesday in Puerto Rico, according to LUMA Energy which provides electricity to the US island territory.
"We will conduct field inspections as soon as it is safe for our crews to go out into the field to identify damage and begin repairs," LUMA said in a statement.
The company said it would prioritise restoring power to essential services such as hospitals and water and sewage facilities.
More flood-producing rains were falling on the US Virgin Islands and Puerto Rico, the hurricane centre said, warning that floodwaters were covering some streets and causing mudslides.
"I urge you to stay safe in your homes, have the emergency numbers at hand and follow the recommendations of the official authorities. The safety of everyone is a priority," Puerto Rico governor Pedro Pierluisi said on X.
Puerto Rico and Virgin Island schools were closed on Wednesday, as were many governmental offices.
