Charley, already packing winds of up to 110 mph, was expected to strengthen and hit the Tampa Bay area late Friday, dumping heavy rain and possibly spawning tornadoes, according to the Associated Press.
The eye of the storm passed west of the Florida Keys on Friday morning but only minor damage was immediately reported.
Earlier, as Charley passed Cuba at its narrowest point, the storm yanked roofs off homes, downed power lines and battered Havana with high wind and heavy rain. There were no immediate reports of casualties.
Cuban President Fidel Castro, who turned 78 Friday, discussed Charley's advance for an hour after midnight on a live television broadcast, expressing relief that Havana escaped the brunt of the storm.
"This was like a birthday present from Nature, a special present, because a hurricane can cause most damage in a capital city, to housing, industry and electricity lines," he said, Reuters reported.
The hurricane arrived in Florida a day after Tropical Storm Bonnie came ashore at the Florida Panhandle and quickly headed north, hitting parts of the East Coast with severe storms and tornadoes.
Three people, including a child, were killed and 25 injured Friday when a tornado hit a trailer park in eastern North Carolina.
In Florida, about 6.5 million residents -- including 700,000 elderly people -- out of the state's total 17 million population were in Charley's projected path, according to U.S. Census Bureau figures.
About 1.9 million people from the Florida Keys and along the state's west coast were advised to evacuate, although only 1.1 million to 1.5 million were expected to do so before the storm hits, Kristy Campbell, spokeswoman at the state emergency management center, told the AP.
The evacuation order was Florida's largest since 1999 when Hurricane Floyd prompted an order for a record 1.3 million people to evacuate the state's east coast, said Craig Fugate, the state's emergency director.
Gov. Jeb Bush urged people in evacuation areas to leave and warned inland residents that they still may be battered by hurricane force winds.