Jaime Sarbaugh, an emergency management spokeswoman for Collier County, where the storm first hit, told Reuters, "The rain is coming down sideways. We've had a handful of tornadoes."
The Category 3 storm, which had weakened after three days in the Mexican resort towns of Cancun and Cozumel, regained strength as it made landfall at dawn then roared across Miami, Ft. Lauderdale and West Palm Beach.
At least one death has been blamed on the storm in Florida, the Associated Press reported. Another 17 people in the Caribbean also died as a result of the storm.
"We have been huddled in the living room trying to stay away from the windows. It got pretty violent out there for a while," Eddie Kenny told the AP, from his parents home in Plantation where he and his wife took shelter. "We have trees down all over the place and two fences have been totally demolished, crushed, gone."
Experts worried that the east coast of the Florida, which had been less prepared than the western part of the state, could suffer serious damage as the storm maintained much of its punch as it moved across the state.
The National Hurricane Center estimated up to 10 inches of rain and tornadoes for parts of central and southern Florida Monday, and an estimated 630,000 people were without power, Florida Power & Light reported.
In Key West, the popular tourist destination in the Florida Keys, waves crashed ashore and water flooded highways and the downtown area. Though only about 7 percent of the Keys' 80,000 residents evacuated ahead of the storm, no deaths were reported, Key West Police Chief Bill Maudlin told Reuters.
The 2005 Atlantic hurricane season is the busiest on record, according to officials and has produced three of the most intense storms. At one point, as it formed in the Caribbean, Wilma became the most powerful storm on record in the Atlantic.
As Wilma plowed through the Caribbean last week, Haiti saw the most casualties with 10 people dead. Seven people died in Mexico, fewer than officials feared, Reuters reported.
In Cuba, where Wilma knocked over lamp posts and smashed windows with 86-mph wind gusts residents hid indoors. "We haven't seen it this bad in years," Havana resident Alfredo Suarez told Reuters.
Late Monday morning, Wilma lost some of its power and became a Category 2 hurricane. The storm is expected to move across Florida at 25-mph and head northeast into the Atlantic toward Canada.