Wilma marked a Category 5 hurricane early Wednesday with 175 mph (282 kph) winds, and forecasters said a key reading of the storm's pressure showed it to be the most powerful of the year.
Wilma was dumping rain on Central America and Mexico, and forecasters warned of a "significant threat" to Florida by the weekend.
The storm's power multiplied greatly over the last day. It was only Tuesday morning that Wilma grew from a tropical storm into a weak hurricane with 80 mph (129 kph) winds.
At 2:30 a.m. (0630 GMT), U.S. Air Force reconnaissance planes measured Wilma's top sustained winds at 175 mph (282 kph), making it a Category 5 hurricane, according to the National Hurricane Center in Miami. Just two hours earlier, Wilma had been declared a Category 4 storm with maximum sustained winds of 150 mph ( 241 kph).
Wilma's pressure readings Wednesday morning indicated that it was the strongest hurricane of the season, said Trisha Wallace, a meteorologist at the National Hurricane Center in Miami. Wilma had a reading of 892 millibars, the same reading as a devastating unnamed hurricane that hit the Florida Keys in 1935.
"We do not know how long it will maintain this Category 5 state," Wallace said.
Jamaica, Cuba, Nicaragua and Honduras were getting heavy rain from the storm, though it wasn't likely to make landfall in any of those countries, she said. Forecasts showed it would likely turn toward the narrow Yucatan Channel between Cuba and Mexico's Cancun region then move into the storm-weary Gulf.
"It does look like it poses a significant threat to Florida by the weekend. Of course, these are four- and five-day forecasts, so things can change," said Dan Brown, a meteorologist at the U.S. National Hurricane Center.
Wilma's track could take it near Punta Gorda on Florida's southwestern Gulf Coast and other areas in the state hit by Hurricane Charley, a Category 4 storm, in August 2004; forecasters urged Florida residents to closely monitor Wilma.
The state has seen seven hurricanes hit or pass close by since August 2004, causing more than $20 billion in estimated damage and killing nearly 150 people, reports the AP.