The National Hurricane Centre has said Irma is likely to approach Florida by Sunday.
And the Prime Minister has committed to protecting UK citizens in the region following criticism of her Government’s approach to the destruction caused by the hurricane in the British Virgin Islands.
After an emergency Cobra meeting, Mrs May said: “I heard directly from our consul general in Miami about the support that is being given to British nationals living in Florida and also British tourists in Florida.
“We are, of course, working with the US authorities to ensure that every support is available and everything can be done before Hurricane Irma reaches Florida.”
The Government has also increased funding for disaster relief in British overseas territories to £32 million.
Five of the 22 people reported to have died during Irma’s initial landfalls are said to have come from the British overseas territories of the British Virgin Islands and Anguilla.
However, the Government has faced criticism for its handling of the crisis.
The Chairs of the Common’s Foreign Affairs and International Development Committees, Tom Tugendhat and Stephen Twigg, said Britain’s response has been “found wanting”.
In a letter to Foreign Secretary Boris Johnson and International Development Secretary Priti Patel, they said: “While we welcome the increase in funding for disaster relief in the British Overseas Territories to £32 million and the fact that personnel, equipment and the RFA Mounts Bay were dispatched to the area before the hurricane struck, arriving in Anguilla the day after its devastation, we are concerned that many in the UK’s overseas territories in the Caribbean are still in grave need.”
Emergency services in Florida have warned residents they will stop answering to calls once Hurricane Irma’s deadly winds hit the state.
Pasco County public safety administrator Kevin Guthrie said: “If you have a heart attack, if you have a stroke, if you have some type of medical emergency, we will not come and help you.
“The emergency management standard is that once tropical storm force-winds get to 40 or 45 mph and are sustained for one minute or longer, your emergency services department ceases to respond to calls for service.
“We are asking people to go to a loved one’s house, evacuate the area, heed our warnings.”
The county is located in one of the areas expected to be hit by Hurricane Irma’s devastating force.