Hurricane Irma barrels towards the Caribbean and Florida

Islanders brace for possible life-threatening winds, storm surges and flooding

People buy wood panels at a hardware store in Puerto Rico in preparation for Irma. Alvin Baez / Reuters

Hurricane Irma, a powerful Category 4 storm, ploughed towards the Caribbean and the southern United States on Tuesday as islands in its path braced for possible life-threatening winds, storm surges and flooding.

Hurricane warnings and watches were in effect for territories in the region, including parts of the Leeward Islands, the British and US Virgin Islands and Puerto Rico, in preparation for a storm that was intensifying with 220kph winds, the US National Hurricane Centre (NHC) said.

The US National Weather Service said on Monday preparations should be rushed to completion as tropical storm-force winds were due to arrive "by late Tuesday".

A Category 4 hurricane on the five-step Saffir-Simpson scale means sustained winds of 209-251kph with "catastrophic" outcomes, including uprooted trees, downed power lines and water and electricity outages.

The Miami-based hurricane centre also warned Category 4 storms can cause significant property damage causing uninhabitable conditions.

In preparation for the storm, the Puerto Rico government declared a state of emergency and activated its National Guard on Monday. The US territory has 456 emergency shelters prepared to house up to 62,100 people.

Puerto Rico also activated a price freeze on basic necessities, including food and water, medicines, power generators and batteries, to help residents prepare.

Telemundo TV station WIPR in Puerto Rico showed long lines of shoppers stocking up on bottled water, flashlights, batteries, generators, food and other items.

The executive director of the state power authority, Ricardo Ramos, said the power grid was so vulnerable from lack of investment that parts of the territory could be without power for three to four months.

"We're preparing for the worst-case scenario," he said.

Irma also threatens Florida and further north along the US east coast, which declared a state of emergency on Monday night. The hurricane centre expects Irma to reach southern Florida on Saturday.

Florida governor Rick Scott said he had spoken to US president Donald Trump, who he said "offered the full resources of the federal government as Floridians prepare for Hurricane Irma".

The NHC cautioned that it was too early to forecast the storm's exact path or what effects it might have on the mainland US, but warned of likely effects to hit some areas by later this week.

"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 US coast by later this week," the centre said.

Irma will be the second powerful hurricane to thrash the US in as many weeks.

Residents of Texas and Louisiana are still reeling from the catastrophic effects of the deadly Hurricane Harvey, which struck Texas as a Category 4 hurricane on August 25.

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