Hurricane Jose seen weakening on Sunday - NHC

Irma was projected to retain much of its strength as it headed up the west coast; since it will remain on or close to the coast, it will be able to recharge power from unusually warm waters in the Gulf.

With Hurricane Irma making its way towards South Florida, properties in the area have been evacuated, and that includes Donald Trump's Mar-a-Lago resort.

Storm surge is an "abnormal rise of water generated by a storm, over and above the predicted astronomical tides", according to the National Oceanic and Atmospheric Administration (NOAA).

The Category 5 storm had maximum sustained wind speeds of 160mph on Saturday, according to the US National Hurricane Centre. It's possible that Irma will be the worst storm to ever hit the Keys. Winds were so intense they reportedly damaged the gauge used to measure them.

The power outages are expected to increase as the storm edges further north. "So it's going to take a while". Still a large hurricane, its tropical storm force winds extend out 415 miles, despite weakening a bit more to 100 mph.

More than 1,100 police, military officials and others were deployed to St Martin and the nearby French Caribbean territory of St Barts, where they used helicopters to identify the cars of people looting stores and homes.

Hurricane Irma has hit Florida as a Category 4 storm after causing major destruction in Cuba.

McMaster considered ordering a mandatory evacuation through the end of the week but relented late Friday, saying he would only require barrier islands in Colleton, Beaufort and Jasper counties to clear out.

Tornadoes may also form Saturday and Sunday over the southern part of Florida, forecasters said.

Monroe County Administrator Roman Gastesi says relief will arrive on a C-130 military plane Monday morning at the Key West International Airport. So, too, are the possibility of quick spin-up tornadoes. "Florida residents can expect widespread wind damage with long term power loss and localized flooding with 5-10" of rain (up to 20" in spots) along with the threat for weak, isolated tornadoes.

The Foreign and Commonwealth Office said the "situation could deteriorate significantly" and its "ability to provide assistance may be extremely limited".

  • Joanne Flowers