Hurricane Joaquin strengthened as it battered the Bahamas with torrential rains, storm surges and heavy winds on Thursday and US officials raced to prepare for possible landfall early next week, three years after Superstorm Sandy devastated New York and New Jersey.
Joaquin, the third hurricane of the 2015 Atlantic season, intensified into a major Category 4 storm on a scale of 1 to 5, with maximum sustained winds of 130 miles (209 km) per hour, the US National Hurricane Center said.
US energy installations in the Gulf of Mexico were unaffected by the storm.
While forecasts of the storm's trajectory were still uncertain, Joaquin was the first tropical cyclone to potentially threaten the US northeast since Sandy.
Several computer models showed Joaquin approaching the coast of the Carolinas by the weekend, then losing strength as it moves offshore past Delaware and New Jersey early next week to head toward Long Island and New England.
One often reliable European model indicated the storm may cut a path out to sea, but the governors of New York, Connecticut and New Jersey - where Sandy killed more than 120 people and caused some $70 billion in property damage in October 2012 - warned residents to prepare for a possible severe storm.
New Jersey Governor, Chris Christie declared a state of emergency on Thursday, adding he would consider ordering evacuations. The governors of Virginia and North Carolina have also declared states of emergency.
"We're hoping for the best, but hope is not preparation nor is it a plan," North Carolina Governor Pat McCrory said in a statement on Thursday.
"I've ordered all state agencies to begin preparation for the severe weather, particularly flooding, that is going hit just about every corner of the state during the next few days."
One person died after several cars were submerged in flash floods in South Carolina, local media reported on Thursday.
Some additional strengthening of Joaquin was possible over the next day, as it approaches parts of the central and northwest Bahamas, the Miami-based NHC said.
The storm's eye was passing over uninhabited Samana Cay Thursday, moving southwest at 6 mph (9 kph) and threatening resorts on the smaller islands of San Salvador, Exuma and Cat Island.
Joaquin's hurricane-force winds were forecast to miss the larger Bahamas islands and the main cities and cruise ship ports of Freeport and Nassau.
Storm surges will push water as high as 5 to 10 feet (1.5 to 3 meters) above normal tide levels in the central Bahamas, the NHC said, with up to 20 inches (51 cm) of rain possible in some areas.
Residents on the Bahamas islands closest to Joaquin's path, which include Rum Cay, Long Island, Exuma and Eleuthera, had stocked up on food and drink, and were boarding up homes and businesses.
In North Carolina's vulnerable Outer Banks, a strip of barrier islands linked by road, some vacationers decided to pack up early and leave before the weekend.
"Everybody is taking this one a little more seriously because of the rain we have had," said Hyde County commissioner John Fletcher on Ocracoke Island, noting heavy rain had saturated the area in recent days.
US energy companies said they had learned from Sandy and used the last three years to gird their oil, natural gas and power infrastructure to better withstand another storm.
Consolidated Edison Inc, which supplies power, gas and steam to more than three million customers in the New York City area, said it was three years into a four-year $2 billion plan to strengthen its infrastructure after Sandy shut down the Big Apple.
Sandy, the worst storm in Con Edison's history, left about a million customers without power, with outages lasting a couple of weeks in the hardest hit areas. Some customers of other utilities were without power for much longer.