Islands in the Caribbean have made last-minute preparations for Hurricane Irma, the most powerful Atlantic storm in a decade, with officials warning of its "potentially catastrophic" effects.
The category five hurricane, the highest possible level, has sustained wind speeds reaching 295km/h (185mph).
It is starting to hit the Leeward Islands and will move on towards Puerto Rico and the Dominican Republic.
In the US, Florida's Key West area has ordered a mandatory evacuation.
Visitors will be required to leave on Wednesday morning, with residents due to follow in the evening, and the international airport will halt all flights.
"We're emphatically telling people you must evacuate. You cannot afford to stay on an island with a category five hurricane coming at you," said Martin Senterfitt, the emergency operations centre director in Monroe County in Florida.
Closer to the storm, thousands of people have been evacuated from at-risk areas. Residents have flocked to shops for food, water, and emergency supplies, and in several locations goods were already in short supply.
Airports have closed on several islands, popular holiday destinations, and authorities have urged people to go to public shelters.
US President Donald Trump has declared a state of emergency for Florida, Puerto Rico and the US Virgin Islands, mobilizing federal disaster relief efforts for those areas.
In Puerto Rico, a 75-year-old man died during preparations for the storm, which has been described by Governor Ricardo Rossello as "something without precedent".
Storm surges, life-threatening winds and torrential rainfall are expected along the Leeward Islands, which include Antigua, Barbuda and Anguilla.
Alison Strand, originally from Staffordshire in the UK, is on the island of Anguilla. She said her family had spent the last several hours fortifying her home on the coast, which "will be the first house hit by the storm".
"Our house is 5m (15ft) above sea level and we're expecting 8m swells, so we're just crossing our fingers," she said. "We are expecting to lose our wooden roof."
Gary Randall, head of the Blue Waters Resort on Antigua's north coast, said: "I wasn't that nervous yesterday, but today I'm nervous."
Staff had boarded up windows, stripped trees of coconuts to stop them damaging property and secured anything that could become a hazard.