The director of the National Hurricane Center says Hurricane Dennis will have a "tremendous impact" well away from its center.
Top winds are at 145 miles an hour, making Dennis a strong Category Four storm. The hurricane center's Max Mayfield says it's "much worse" than a Category Three.
Dennis will strike the Gulf Coast this afternoon somewhere along the coast of the Florida Panhandle, Alabama or Mississippi. But hurricane force winds are likely to hit even sooner. It could dump a half-foot of rain and cause a 17-foot storm surge in the same area pounded by Hurricane Ivan last September.
Hurricane Dennis is blamed for at least 20 deaths in Haiti and Cuba.
It also toppled trees and flooded streets in the Florida Keys and has spun off tornadoes in the Tampa area.