Hurricane Ian has become an extremely dangerous Category 4 storm as it approaches Florida’s west coast, forecasters said.

The US National Hurricane Centre in Miami said at 5am local time on Wednesday that Ian now has top sustained winds of 140mph and is centred about 75 miles west-southwest of Naples, Florida.

It said Ian is moving north at a forward speed of 10mph.

The major hurricane has prompted warnings of possibly dangerous storm surge along the state’s heavily populated Gulf Coast from Bonita Beach to the Tampa Bay region.

Winds and rain have begun intensifying, a day after Ian battered the western tip of Cuba, bringing down the electricity grid and leaving the entire island without power.

Florida residents rushed to board up their homes, stash precious belongings on upper floors and flee.

“You can’t do anything about natural disasters,” said Vinod Nair, who drove inland from the Tampa area on Tuesday with his wife, son, dog and two kittens seeking a hotel in the tourist district of Orlando.

“We live in a high risk zone, so we thought it best to evacuate.”

Mr Nair and his family were among at least 2.5 million Florida residents ordered to evacuate in anticipation of a powerful storm surge, high winds and flooding rains.

The hurricane centre predicted Ian would roar ashore on Florida’s south-west coast on Wednesday afternoon.

Winds exceeding tropical-storm strength of 39mph reached Florida by 3am local time and hurricane-force winds were expected in Florida well in advance of the eyewall moving inland, the Miami-based centre said.

“It is a big storm, it is going to kick up a lot of water as it comes in,” Florida governor Ron DeSantis said in Sarasota, a coastal city of 57,000 in the storm’s projected path.

He warned at a news conference: “This is the kind of storm surge that is life threatening.”

Ian’s forward movement slowed over the Gulf, enabling the hurricane to grow wider and stronger.

A hurricane warning covering roughly 220 miles of the state included Fort Myers as well as Tampa and St Petersburg, which could get their first direct hit by a major hurricane since 1921.

Forecasters said the storm surge could reach 12ft (3.6 metres) if it peaks at high tide.

Rainfall near the area of landfall could top 18in (46 centimetres).

Gil Gonzalez was not taking any chances.

He boarded the windows of his Tampa home with plywood and laid down sandbags to guard against any flooding.

He and his wife packed their car with bottled water, torches, battery packs for their mobile phones and a camp stove before evacuating.

“All the prized possessions, we’ve put them upstairs in a friend’s house,” Mr Gonzalez said.

Airports in Tampa, St Petersburg and Key West closed.

Disney World theme parks and Sea World in Orlando all closed ahead of the storm.

A couple from England on holiday in Tampa found themselves faced with riding out the storm at a shelter.

Glyn and Christine Williams, from London, were told to leave their hotel near the beach when evacuations were ordered.

Because the airport shut down, they could not get a flight home.

“Unfortunately, all the hotels are full or closed, so it looks as though we’re going to be in one of the shelters,” Christine Williams said.

Her husband insisted all would be fine.

“You know, you got to go with the flow,” Glyn Williams said.

“So we’re quite happy doing what we’re doing.”

The precise location of landfall was still uncertain, but with Ian’s tropical storm-force winds extending 175 miles from its centre, damage was expected across a wide area of Florida.

Flash floods were possible across the whole state, and portions of its east coast faced a potential storm surge threat as Ian’s bands approach the Atlantic Ocean.

Warnings were also issued for isolated tornadoes.

Florida Power and Light warned those in Ian’s path to brace for days without electricity.

As a precaution, hundreds of residents were being evacuated from several nursing homes in the Tampa area, where hospitals were also moving some patients.

Parts of Georgia and South Carolina could also see flooding rains and some coastal surge into Saturday.

Georgia governor Brian Kemp pre-emptively declared an emergency, ordering 500 National Guard troops on to standby to respond as needed.

Before turning towards Florida, Ian struck Cuba’s Pinar del Rio province with sustained winds of 125mph, causing destruction in the island nation’s world-famous tobacco belt.

Local government station TelePinar reported heavy damage at the main hospital in Pinar del Rio city, tweeting photos of collapsed ceilings, widely flung debris and toppled trees.

No deaths were reported.

Some left the stricken area on foot, carrying their children, while buses tried to evacuate others through waterlogged streets.

Others opted to stay at their damaged houses.

“It was horrible,” said Yusimi Palacios, a resident of Pinar del Rio inside her damaged house.

“But here we are alive, and I only ask the Cuban revolution to help me with the roof and the mattress.”