Severe Hurricane Irma has now become a powerful Category 5 storm on the five point Saffir-Simpson Scale.

Packing winds of 240 km per hour (kph), and gusts nearer 300 kph, Hurricane Irma ploughed towards the Leeward Islands and the southern United States on Tuesday as islands in its path braced for possible life-threatening winds, storm surges and flooding.

A state of emergency has been declared from the northern portions of the Lesser Antilles extending right across the state of Florida.

Hurricane Irma is currently located around 500km to the east of Antigua. The system is moving west at approximately 22kmph and is expected to pass close to the northern Leeward Islands on Tuesday night and Wednesday morning.

This is a dangerous and major hurricane, accompanied by life-threatening winds, torrential rain, and a large storm surge.

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Irma is expected to remain as a Category 5 hurricane right through to the weekend.

"This is not an opportunity to go outside and try to have fun with a hurricane," US Virgin Islands Governor Kenneth Mapp warned.

"It's not time to get on a surfboard."

Some areas are likely to see 200mm to 300mm of rain. Similarly, such rainfall amounts could cause life-threatening flash floods and mudslides.

Once the storm clears the Leeward Islands, the violent winds are expected to affect the British and US Virgin Islands along with Puerto Rico. After that, Hispaniola, Cuba and the Bahamas could also feel its impact.

There is currently an area of low pressure producing a band of rain across central parts of the US. If that continues to make its way towards the eastern seaboard, it should help steer Irma back into the open waters of the North Atlantic.

The alternative could see flooding and wind damage anywhere from the Panhandle to the Mid-Atlantic States, and possibly further north.

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

Harvey, which came ashore on August 25 as the most powerful hurricane to hit Texas in 50 years, killed an estimated 47 people and displaced more than one million after causing wreckage in an area stretching for nearly 500km.

US President Donald Trump asked Congress to approve $7.85bn in initial emergency funding to deal with the devastation wrought by Hurricane Harvey.