Hurricane Wilma's march toward Florida slowed somewhat, giving residents an unexpected extra day to prepare for the storm, while authorities stockpiled emergency supplies.
Max Mayfield, director of the National Hurricane Center, said the slowdown would likely weaken the storm from a Category 4, with sustained 241 kph winds, to a Category 3 or less before making landfall in the United States.
Mayfield said Wilma is unusually large, with tropical storm-force winds extending out some 418 kilometers from the center that could cause widespread damage.
State meteorologist Ben Nelson warned that Wilma could produce a storm surge of 3.6 to 5.1 meters.
At 8 p.m. EDT Wilma was heading northwest at near 8 kph toward Mexico's Yucatan Peninsula, where Mayfield said it could do catastrophic damage.
The storm had strengthened slightly, and forecasters said it could regain Category 5 strength winds of 251 kph or more.
Although Wilma was expected to approach from the west, forecasters warned that major Atlantic Coast cities including Miami, Fort Lauderdale and West Palm Beach could be hit by strong winds and heavy rains.