Hurricane Irma is lashing Cuba with strong winds and heavy rain after devastating several Caribbean islands.
The hurricane made landfall on the Camaguey Archipelago, in Cuba's north-east, as a category five storm.
But the Bahamas have largely been spared after Irma changed track.
In Florida, 5.6 million people, or 25% of the US state's population, have been told to leave as the storm approaches. At least 20 people are known to have died so far across the Caribbean.
Irma hit the Camaguey Archipelago late on Friday, threatening nearby coastal towns and villages.
It was the first category five hurricane to hit Cuba in decades, although it had weakened to category four by Saturday morning.
At 09:00 GMT, Irma had maximum sustained winds of 249km/h (155mph), the National Hurricane Center in the US said.
A hurricane warning is currently in effect in the provinces of Camaguey, Ciego de Avila, Sancti Spiritus, Villa Clara and Matanzas, while floods have been reported in the north-east.
Some communities have lost power, and communication is becoming increasingly difficult with towns in more remote areas, the BBC's Will Grant in Havana reports.
Cuban officials reported "significant damage", without giving further details, but said there were no confirmed casualties yet, AFP news agency reported.
Residents are hoping the storm will just glance the island before heading across the Florida Straits.
Earlier, people tried to secure their roofs and move belongings from low-lying coastal areas to higher ground.
"There are really strong gusts of wind. It is pouring off and on, and the lights are out," Anaida Gonzalez, a retired nurse in the Camaguey province, told Reuters.
About 50,000 tourists are fleeing or have fled Cuba, with resorts on the north coast now empty, the news agency reports.
Irma is expected to hit Florida on Sunday.
Brock Long, the head of the US federal emergency agency, warned that Irma would "devastate" either Florida or neighbouring states.
He said that parts of Florida would be without power for days.
"The entire south-eastern United States better wake up and pay attention," he added.
Florida Governor Rick Scott said all Floridians should be prepared for possible evacuation, and issued a stark warning to those in threatened areas.
"We are running out of time. If you are in an evacuation zone, you need to go now," he told reporters.
"Remember, we can rebuild your home, we can't rebuild your life."
The death toll continued to rise on Friday in the Caribbean.
France's Interior Minister Gérard Collomb said nine people were dead and seven missing in the French territory on St Martin, an island shared with the Netherlands, and St Barthélemy.
Another death - the second - has been confirmed in the Dutch territory of Sint Maarten.
French officials said six out of 10 homes on Saint-Martin were so badly damaged that they were uninhabitable.
US President Donald Trump spoke on Friday to his French counterpart Emmanuel Macron to extend his condolences and offer support, the White House said.
French, British and Dutch military authorities have deployed aid - including warships and planes equipped with food, water and troops - to their territories.
Which other areas have already been hit?
- Turks and Caicos Islands: widespread damage, although extent unclear
- Barbuda: the small island is said to be "barely habitable", with 95% of the buildings damaged. Antigua and Barbuda Prime Minister Gaston Browne estimates reconstruction will cost $100m (£80m). One death has been confirmed
- Anguilla: extensive damage with one person confirmed dead
- Puerto Rico: more than 6,000 residents of the US territory are in shelters and many more without power. At least three people have died
- British Virgin Islands: widespread damage reported
- US Virgin Islands: damage to infrastructure was said to be widespread, with four deaths confirmed
- Haiti and the Dominican Republic: Both battered by the storm, but neither had as much damage as initially feared
- Are there more hurricanes to come?
- Another storm, Jose, further out in the Atlantic behind Irma, is now a category four hurricane, with winds of up to 240km/h (150mph).
- It is following a similar path to Irma and already hampering relief efforts in some of the worst affected areas.
- Residents of Barbuda, where 95% of buildings have been destroyed by Irma, have now left the island as Jose approaches.
- Hurricane Katia, in the Gulf of Mexico, a category one storm with winds of up to 75mph, made landfall on the Mexican Gulf coast in the state of Veracruz late on Friday.
- The storm is expected to weaken rapidly in the coming hours.