KEY WEST, Fla. — Residents boarded up windows yesterday and evacuated the low-lying Florida Keys as Tropical Storm Rita gathered strength in the Bahamas, threatening to grow into a hurricane with a potential 8-foot storm surge.

The storm had top sustained winds of 70 mph yesterday evening, and it was expected to strengthen into a Category 1 hurricane, with winds of at least 74 mph, by the time it approached the Keys early today.

Hurricane warnings were posted for the Keys and Miami-Dade County, according to the National Hurricane Center in Miami. Residents and visitors were ordered to clear out of the entire chain of islands, connected by just one highway. Voluntary evacuation orders were posted for 134,000 Miami-Dade residents of coastal areas such as Miami Beach.

While many Keys residents take pride in staying put during hurricanes, others said they were worried because of Katrina's devastation of Louisiana and Mississippi. Most stores on Key West's Duval Street were boarded up yesterday, and streets were nearly empty.

Gov. Jeb Bush said yesterday the highway patrol reported that traffic out of the Keys was moving well on U.S. 1.

Long-range forecasts can be off by hundreds of miles, but hurricane-center forecasters warned people along the Gulf Coast to watch Rita closely; officials in Galveston, Texas — nearly 900 miles from Key West — were already calling for a voluntary evacuation there. Forecasters said Rita could be near Mexico or Texas by the weekend, with a possibility that it could turn toward Louisiana.

"This is something everyone should be paying attention to," said Daniel Brown, a hurricane-center meteorologist. Katrina had crossed South Florida into the Gulf of Mexico last month before hitting Louisiana and Mississippi.