Wilma hit the state as surprisingly strong Category 3 hurricane after feeding for days over the warm waters of the Gulf of Mexico. It later weakened to a Category 2 as it raced across the state in about four hours, but dealt a harsh blow.
A man died when a tree fell on him in the Fort Lauderdale suburb of Coral Springs, local officials said. The storm knocked out electricity to more than 3 million people, as it blasted beach sand across coastal roads and shredded power lines.
Wilma had weakened after hammering Cancun and Cozumel in Mexico for three days, but revved up to reach Florida with 125 mph (200 kph) winds. The winds slowed to 105 mph (170 kph) as it crossed the state.
The storm's power startled thousands of people in the vulnerable, low-lying Florida Keys who ignored evacuation orders.
Although the eye moved north of Key West, a powerful storm surge that in places had been expected to reach 18 feet (5.5 metres) washed through the Keys and left much of the tourist town made famous by writer Ernest Hemingway under water.
"There is massive flooding from tip to tip, 3 to 5 feet (1-1.5 metres) of water," Key West Mayor Morgan McPherson said.
Wilma lashed Cuba on its way east, paralysing Havana and flooding coastal neighbourhoods.
The eighth storm to hit Florida in the last 15 months, Wilma struck the mainland before dawn on the west coast near Naples and sped across the Everglades to the populous east coast, pounding Miami, Fort Lauderdale and West Palm Beach, an area of 5 million people.
The worst of the storm's tidal surge struck a largely unpopulated area south of Naples. Search-and-rescue efforts were focused on Marco Island and Everglades City, two populated areas near Wilma's center, state officials said.
The sprawling storm, about 400 miles (645 km) across, covered much of the Florida peninsula. Some of its strongest winds whipped greater Miami, which alone had about 1.2 million customers, or 2.4 million people, without electricity, according to Florida Power & Light.
The company said it had 1.6 million customers without power in the state and had shut down three nuclear reactors.
Forecasters said Wilma, at one point the strongest Atlantic hurricane on record, could prove to be the strongest storm in Miami since Hurricane Andrew caused more than $25 billion in damage in August 1992.
By 11 am (1400 GMT), Wilma's center had begun to move over the Atlantic Ocean off West Palm Beach and was heading north-east at about 25 mph (40 kph).
Wilma was the eighth hurricane to strike Florida in about 15 months - an unprecedented display of nature's fury.
The 2005 Atlantic hurricane season, which ends on November 30, became the busiest since records began 150 years ago with the formation on Saturday of the 22nd named tropical cyclone, Alpha.
It also boasts three of the most-intense Atlantic storms on record, with Katrina, which devastated New Orleans in August and killed 1,200, Rita, which hit the Texas-Louisiana border a few weeks later, and now Wilma, the storm with the lowest barometric pressure reading ever observed in the Atlantic.
In Mexico, Wilma caused severe damage in Cancun and on the island of Cozumel off the Yucatan.
Many of the 20,000 or more tourists stranded on the "Maya Riviera" were short of food and water.
The storm killed seven people in Mexico, fewer than many had feared. It killed 10 people in Haiti last week after spawning mudslides in the impoverished Caribbean country.
In Cuba, 86-mph (138-kph) wind gusts howled through Havana, knocking down lamp posts and smashing windows.