Cheerleaders at an American football game between the New York Giants and the New Orleans Saints in East Rutherford, New Jersey. (AFP)

Miami, Sept. 20 (Reuters): Tropical Storm Rita strengthened into a hurricane today and lashed the low-lying islands of the Florida Keys with gusty squalls and heavy rain.

All 80,000 residents had been ordered out of the Keys yesterday but many stayed behind in boarded-up homes to await Rita’s arrival. The hurricane was expected to strengthen further as it moves into the Gulf of Mexico where deadly Hurricane Katrina wreaked havoc three weeks ago.

“It’s raining pretty hard (but) there’s no big wind yet,” said Keys resident Mare Contrare, who protected her house with aluminum sheets. Contrare said it seemed too early to judge whether staying in the storm’s path had been a mistake. “At this point it seems fine,” she said.

Miami-Dade mayor Carlos Alvarez cautioned southern Florida not to dismiss the power of the coming storm, which sent intermittent squalls over the Miami area as the main core neared the Keys.

“Stay home. No matter what, we’re going to have lousy weather,” he said. Schools, many government offices and some businesses were closed today.

Oil companies only starting to recover from Katrina evacuated Gulf oil rigs. Private forecasters said there was a 40 per cent chance that damaging hurricane-force winds would directly affect major Gulf energy production areas.

Rita was the 17th tropical storm of an exceptionally busy Atlantic hurricane season became a hurricane when its sustained winds strengthened to 119 kmph.

It was expected become a major hurricane with sustained winds of at least 178 kmph, said the US National Hurricane Center in Miami.

Rita’s center was about 160 km east-southeast of Key West, Florida.