Officials in Florida's Key West and popular Caribbean tourist islands ordered people to evacuate on Tuesday as Irma, a "potentially catastrophic" Category Five hurricane, was set to make landfall.
The monster hurricane coming on the heels of Harvey, which struck Texas and Louisiana late last month, is expected to hit a string of French islands including Guadeloupe late Tuesday before heading to Haiti and Florida.
The Miami-based National Hurricane Center said Irma had strengthened to the most powerful Category Five, packing winds of 180 miles (280 kilometers) per hour.
The front was moving west at 14 miles (22 kilometers) per hour, and is expected to dump up to 18 inches (45 centimeters) of rain in some areas when it hits land.
"These rainfall amounts may cause life-threatening flash floods and mudslides," the NHC warned, calling the storm "potentially catastrophic" and urging that "preparations should be rushed to completion" in the region.
Schools and government offices in Guadeloupe have been ordered shut, while hospitals are stocking up on medicines, food and drinking water. People living on shorelines will be moved to safety, authorities said.
Saint Barthelemy and Saint Martin islands, both popular holiday destinations, are expected to be especially hard hit.
The Dutch defense minister said soldiers arrived in the Dutch part of Saint Martin on Monday and two vessels, including one equipped with a helicopter, were in place to help.
Officials had on Monday ordered the evacuation of 11,000 people living in affected areas on both islands, which began in many neighbourhoods on Tuesday, an AFP correspondent said.
Threat to Florida
The governor of the US state of Florida, Rick Scott, declared a state of emergency, saying Irma posed "a severe threat to the entire state", barely a week after Harvey claimed at least 42 lives.
He asked President Donald Trump to declare an emergency for the state as well, which would help draw resources to the area to respond to any damage.
Tourists in the popular Key West islands were packing their bags on a mandatory evacuation order and were due to begin leaving at sunrise on Wednesday, with a similar order for residents due to follow.
"We're emphatically telling people you must evacuate, you cannot afford to stay on an island with a Category 5 hurricane coming at you," said Monroe County emergency operations center director Martin Senterfitt.
There were long queues as people rushed to get batteries, bottled water, groceries and fuel, while many cut trees around their homes and sought to tie down objects and seal up their windows.
In a crowded supermarket in Miami Beach where people were scrambling to buy provisions, it was already difficult to find some basic supplies, like water.
Whole shelves stood empty.
"It's because people go crazy and buy up everything," 81-year-old resident Gladys Bosque told AFP.
"They believe the hurricane will last a month when it could pass us by. Look, there's no water, no milk, there are very few cans—and no cat food."
Category Five hurricanes are rare and are capable of inflicting life-threatening winds, storm surges and rainfall.
A hurricane of this magnitude can tear off roofing, shatter windows, uproot palm trees and turn them into projectiles that can kill people.
Irma is projected to bring water levels up to 11 feet (3.3 metres) above normal, rainfall of up to 10 inches (25 cm) in places, and "large and destructive waves," the US National Hurricane Center warned.
Harvey, which dumped as many as 50 inches of rain in parts of Houston, turning neighbourhoods into lakes and causing material damage estimated at around $100 billion (85 billion euros), was a Category Four hurricane.
In Puerto Rico, a US territory of 3.5 million, Governor Ricardo Rossello activated the National Guard and announced the opening of storm shelters able to house up to 62,000 people.
The mayor of the Puerto Rican capital San Juan, Carmen Yulin Cruz Soto, ordered 900 municipal employees—police, emergency personnel, and aid and social workers—to report for rotating 12-hour shifts.
Even if Puerto Rico is spared a direct hit, the mayor said, three days of pounding rain will do heavy damage.
US carrier in position
A US aircraft carrier with a field hospital and dozens of aircraft able to conduct rescue or supply missions have been positioned in the area, according to Alejandro de la Campa of the Caribbean division of the US Federal Emergency Management Agency (FEMA). Local press identified the carrier as the USS Kearsarge.
Irma's precise path remains unclear. But several projections have it passing over the Dominican Republic, Haiti and Cuba before turning north toward Florida and then possibly swinging up the US East Coast.
Explore further: Category Two Hurricane Irma forms in eastern Atlantic