July 8 (Bloomberg) -- Hurricane Dennis strengthened into the strongest storm ever this early in the Atlantic hurricane season, forcing evacuations in parts of the Florida Keys and in Cuba, where coastal areas were flooded.

The hurricane was upgraded yesterday to a Category 4 storm on the five-step Saffir-Simpson scale, and maximum sustained winds blew at 135 miles (210 kilometers) per hour at 8 a.m. Miami time today, the National Hurricane Center said on its Web site. Category 4 storms can tear off roofs, destroy mobile homes and require evacuations 6 miles from shore due to flooding.

``This is the first Category 4 we've ever had in July,'' said Navy meteorologist Lieutenant Dave Roberts at the hurricane center in Miami. ``It's going to bring storm surges and heavy rain, almost like a curtain-wall effect. That's where most of your damage is going to come from.''

Dennis would be only the fourth July hurricane to hit Cuba in 205 years, the official Granma newspaper said today on its Web site. About 200,000 people were evacuated from their homes, all schools were closed for today and flights were suspended in most of the country, Granma said. Haitian authorities said at least one person was killed when the storm passed off the coast.

Florida, which is still recovering and rebuilding after a devastating hurricane season last year, ordered residents evacuated from the southern Keys, said Kristy Campbell, spokeswoman for the state's emergency operation center. Oil companies evacuated rigs and production platforms in the Gulf of Mexico in anticipation of Dennis, which follows in the tracks earlier this week of tropical Storm Cindy.

`Imminent Danger'

At least one man was killed by a falling tree in Les Cayes, southwest Haiti, when the storm passed off the coast, Dieuford Delorge, spokesman for the country's civil protection department said in a phone interview from the capital Port-au-Prince. He said he couldn't confirm an Associated Press report that five people died. Flooding affected areas across the country, and some roofs were blown off homes he said, adding that communication with some parts of Haiti is ``difficult.''

Dennis's center was over the Caribbean Sea south of Cuba's Sancti Spiritus province at 9 a.m. local time, the country's Meteorological Institute said in an advisory on its Web site. The storm was 95 kilometers south-southeast of Trinidad, and heading northwest at 17 kph.

Winds from the storm toppled a television tower in a southeastern province also called Granma, the newspaper said, and roads from the province toward the city of Santiago de Cuba were cut off. Further strengthening will take place as the storm heads northwest before hitting land, Cuba's Meteorological Institute said in an advisory at 6 a.m. local time on its Web site.

Direct Hit

``Hurricane Dennis continues to be a big and imminent danger'' for most of Cuba, the meteorological institute said, adding that the storm surge will be between 3 and 4.5 meters from Casilda to Playa Giron on the south coast. The storm already caused a 4.1-meter storm surge from Guayabal to Jucaro and in Cienfuegos province, leading to coastal flooding in some areas, the institute said earlier.

Dennis will likely hit Cuba later today around the southern provinces of Cienfuegos and Matanzas, according to the Cuban forecast. The center of the storm is then likely to move toward the northwest, crossing the coast of Havana or Matanzas province tonight, before returning to sea, the institute said.

The provinces of Sancti Spiritus and Villa clara, and the capital Havana may also be hit, according to the forecast. Flooding is possible along the north coast, including Havana's Malecon road, the institute said.

Caymans, Florida Keys

Hurricane-force winds extended 50 miles from the center and tropical-storm force winds reached as far as 140 miles out, the U.S. hurricane center said at 5 a.m.

``Dennis is expected to be a very powerful hurricane while crossing Cuba,'' according to the hurricane center in Miami. ``This hurricane will likely cause devastation along its path.''

The center's three-day forecast shows Dennis's eye moving over Cuba today and into the Gulf toward Alabama and Florida. The storm may make landfall in the Florida panhandle by July 11.

``Dennis is forecast to remain as a dangerous Category 4 hurricane while in the Gulf of Mexico,'' the center said.

Alerts

A hurricane warning was in effect for most of Cuba and for the lower Florida Keys from the Seven Mile Bridge west to the Dry Tortugas. A hurricane warning means that winds of more than 73 mph are expected within 24 hours. The Cayman Islands discontinued its hurricane warning in Grand Cayman, and downgraded the alert to a tropical storm warning in other parts of the territory, the U.S. center said.

The evacuated part of the Florida Keys is in Monroe County, which has 84,000 residents, Campbell at the state's emergency operations center said.

A tropical storm warning is in place in Florida along the west coast south of Bonita Beach and along the east coast south of Golden Beach.

A record four hurricanes -- Charley, Frances, Ivan and Jeanne -- struck Florida last year and caused almost $23 billion in property damage.

``We've made great progress rebuilding,'' Campbell said. ``The recovery efforts are still ongoing here. It's too early to predict what the impact of this storm will be.''

Oil companies have evacuated rigs and production platforms in the Gulf of Mexico east of a line from Cameron, Louisiana, 80 miles east of the Texas border. Transocean Inc., the world's largest offshore oil and natural-gas driller, Royal Dutch/Shell Group and Apache Corp. announced evacuations.

Dennis is the fourth-named storm of the Atlantic Ocean hurricane season, its earliest start ever. Dennis became a Category 1 hurricane Wednesday after its winds increased to about 85 mph. The season runs from June 1 to Nov. 30.

Haiti last year was devastated by flooding in May and again in September, when Tropical storm Jeanne killed 3,000 people in the former French colony.

To contact the reporters on this story: Alex Morales in London at amorales2@bloomberg.net. Jessica Brice in San Francisco at jbrice1@bloomberg.net;

Last Updated: July 8, 2005 10:04 EDT