Hurricane Irma left a trail of devastation as it battered several Caribbean islands with 185-mph winds this morning.
The category 5 storm, the most powerful ever recorded in the Atlantic, barred down on St Martin and St Bartélemy in the early hours after causing destruction on Barbuda.
The "extremely dangerous" hurricane is now heading towards the British Virgin Islands where some 30,000 islanders, nearly all British citizens, are bracing for the monster storm.
Winds of 185mph raged on St Martin and videos show widespread flooding and torrential rain.
Brit Alex Woolfall posted a series of frantic tweets from a stairwell on the island.
The Londoner started tweeting at 4.30am local time as the category 5 storm swept towards the beautiful island and he was "evacuated" to the stairs
He described the "apocalyptic" scenes and "constant booms and bangs" as the hurricane took hold.
Irma is now so powerful it has been causing seismic activity as it passes over the Caribbean and is showing on seismometers — the equipment used to measure earthquakes.
The Red Cross has released an initial 120,000 Swiss francs from its Disaster Relief Emergency Fund to help some of the islands affected and volunteers have started making their way to Florida.
Walter Cotte, Americas regional director of the International Committee of the Red Cross, described the forecast as "extremely worrying".
"We are anticipating major impacts on a number of islands, and we are preparing to respond to needs that may arise.
“We are especially worried that Irma could affect areas that have been suffering with severe rainfall in the past months.
“One of the main challenges is going to be logistical, given the isolation of some the islands. We need to ensure a reliable channel for relief efforts in the aftermath of the hurricane.”
The storm is so large it would cover the whole of the "UK and Ireland", according to Channel 4 weather forecaster Liam Dutton.
Some experts say it is about to exceed the maximum theoretical intensity of a hurricane - leading to suggestions a new 'Category 6' should be added to the traditional Saffir-Simpson scale to accommodate it.
Florida residents are now bracing themselves for Irma's arrival at the weekend and shops have already reported running out of water and other essential items.
President Donald Trump tweeted that Irma was looking like the "largest ever" hurricane in the Atlantic.
He added that his administration were watching the storm "closely".
Bahamas prime minister Hubert Minnis has ordered a mandatory evacuation of some islands.
Residents and tourists in Mayaguana, Inagua, Crooked Island, Acklins, Long Cay and Ragged Island will be flown out on Wednesday, just before the storm hits.
Mr Minnis said it will be the largest hurricane evacuation in the history of the Bahamas and anyone who does not leave will be in “great danger”.
The strongest hurricane to ever to make landfall on the US coast was the 'Labor Day' hurricane of 1935, which hit Florida Keys.
Around 500 people were killed and there were reports of bodies being swept from one end of Florida to the other.
Hurricane Andrew, the most recent Category 5 storm, left the Miami-Dade area devastated in 1992.
And since then, the city has transformed, adding huge numbers of residents and reducing the wetlands area which would buffer the storm.
Earlier, business magnet Richard Branson revealed he has decided to remain on his private island in the British Virgin Islands during the storm.
The billionaire says he's survived two hurricanes on the island thanks to his specialised 'hurricane proof' buildings - but says "nothing can withstand" a Category 5 storm.
Branson wrote on his blog: "Generally speaking, we have one hurricane in the British Virgin Islands around every 10 years.
"Fortunately, most of them drift north of us, but this one is coming straight for us, with the eye of the storm heading straight for Necker, Moskito Island and Virgin Gorda.
"Obviously things can change – hopefully they do, as a category five hurricane hasn’t hit the BVI [British Virgin Islands] full on before.
"On Necker Island we have constructed really strong buildings (with hurricane blinds) that should be able to handle extreme weather pretty well, though with a Category 5 hurricane almost nothing can withstand it.
"We had some lovely guests staying on Necker Island who have cut their trip short for safety reasons, and another group of guests have also postponed.
"I will be on Necker alongside our team, as I have been on the three times we have had hurricanes over the past 30 years."
Branson, who said he was on the island in 2010 when it was hit by Hurricanes Earl and Otto, went on to share his concerns for local residents and wildlife.
He added: "In the past, many British Virgin Islanders have shrugged off hurricanes, stayed at home and not gone to shelters.
"This time the BVI Government and the BVI Tourist board have been very active and providing advice to the local population."
Irma is set to hit Necker Island less than two weeks after Hurricane Harvey killed 60 people when it battered the United States and surrounding territories.
Hurricane Irma will reach Leeward Islands, east of Puerto Rico, tonight and could batter Florida by the weekend.
British Airways is already preparing for the worst and flying tourists off the Caribbean island of Antigua.
A BA spokeswoman told Mirror.co.uk: "We have provided a special flight to Antigua to get our customers home before Hurricane Irma arrives on the island.
"The Antigua Airport authorities say that operations will be significantly impacted today, so we have offered all affected customers rebooking options. We are keeping our flights to other Caribbean islands under review."
Florida has declared an emergency and President Donald Trump has "offered the full resources of the federal government as Floridians prepare for Hurricane Irma," reports CNN.
"In Florida, we always prepare for the worst and hope for the best, and while the exact path of Irma is not absolutely known at this time, we cannot afford to not be prepared," said Governor Rick Scott in a statement.
Water is expected to rise 9ft (3metres) above normal levels as the storm brings a predicted 10 inches of rain and "large and destructive waves".
Irma is forecast to strengthen even more over the next 48 hours.
Forecasters say they cannot predict the exact path the storm will take but, islands in Irma's path have been warned to brace themselves in preparation for the intensifying storm that could pummel the area with life-threatening winds and torrential rain.
Hurricane advisories have been issued for territories that dot the West Indies, including the Leeward Islands, the British and US Virgin Islands and Puerto Rico.
Irma was initially a Category 4 hurricane on the five-step Saffir-Simpson scale, meaning sustained winds of 130-156 miles per hour (209-251 kph) with "catastrophic" outcomes.
This includes the uprooting of trees and downed power lines, water and electricity outages, and significant property damage causing uninhabitable conditions, according to the National Hurricane Center.
The NHC said: "There is an increasing chance of seeing some impacts from Irma in the Florida Peninsula and the Florida Keys later this week and this weekend.
"In addition, rough surf and dangerous marine conditions will begin to affect the southeastern U.S. coast by later this week."
Texas and Louisiana residents are still reeling from the catastrophic effects of the deadly Hurricane Harvey.
Harvey struck Texas as a Category 4 hurricane on August 25 and dumped several feet of rain, destroying thousands of homes and businesses.
In preparation for the storm, the economically struggling Puerto Rico government on Monday declared a state of emergency and activated the National Guard.
"Despite the economic challenges Puerto Rico is facing, the approved budget has $15 million for the emergency fund," Governor Ricardo Rosselló said in a statement.
The island of about 3.4 million people has 456 emergency shelters prepared to house up to 62,100 people.
To help residents prepare for the storm, the Puerto Rican government activated a price freeze on basic necessities, including food and water, medicines, power generators and batteries.