Hurricane Dennis slashed across Cuba with 150-mph winds and raged north toward jittery U.S. Gulf Coast, threatening to turn the 2005 Atlantic storm season into a dangerous and record-setting encore to the devastating summer of 2004.

Dennis, whose eye stayed compact and ferocious as its hurricane-force winds stretched 65 miles from its center, could on Sunday become the first major hurricane in seven decades to make landfall in the United States in July, forecasters said, and is one of only seven major hurricanes to occur in July in 150 years of recorded history. Dennis is also the fourth named storm of the season, which started June 1, the most ever at this early stage. "It's extremely unusual," said Dave Nolan, a meteorologist at the University of Miami.

Dennis is already responsible for at least five deaths in Haiti, where flooding exacerbated by deforestation brought new misery to the Western Hemisphere's poorest nation. It shot potent winds at Cuba as its eye passed near the capital, Havana, leaving 10 dead on the island nation. "It's arrived, with all its diabolical force," President Fidel Castro said on state television Friday afternoon.

At 11 p.m., Dennis was 20 miles east of Havana, or about 110 miles south of Key West. It was moving northwest about 14 mph, but its top sustained winds had weakened to 110 mph, making it a Category 2 storm. Forecasters said it could intensify over the Florida Straits.

The storm's rapid evolution from a moderately powerful hurricane into a sprawling giant sent hundreds of thousands of coastal residents -- from the wild weather-seasoned bartenders along the nation's southernmost nub in Key West to the shrimpers in Louisiana's sinking bayous -- into varying stages of alert and anxiety. Tourists, their vacations ruined, turned the gangly two-lane road leading out of the Florida Keys into a miles-long traffic jam and left behind their coveted seaside retreats in Gulf Shores, Ala.

States of emergency were declared by governors across the region, even as forecasters struggled to predict the final destination of a storm made quirky by the competing effects of high pressure to the east that could shove its track west and low pressure over Louisiana and Texas that could nudge it to the northeast. Most forecasters plotted the storm's track toward landfall between Pensacola, Fla., and Mobile, Ala., a route almost identical to last year's behemoth, Ivan, which killed 52 people in the United States and 70 in the Caribbean. About 3,000 people still live in temporary federal housing on Florida's Panhandle and more than 9,200 throughout the state, where thousands of roofs still awaiting repair after four hurricanes last year sit atop the ubiquitous "blue-tarp houses."

Key West, assuming its accustomed role, was first in line as a threatened spot Friday, and police responded by urging tourists to leave.

Shelters opened along the Keys escape route for residents and tourists.

The westward slide of Dennis boded well for NASA, which left the space shuttle Discovery on the launchpad at Cape Canaveral, confident that Dennis would not affect a planned launch on Wednesday, the agency's first since Columbia disintegrated while returning to earth in February 2003. Officials were less optimistic in the New Orleans area, the nation's most vulnerable region during hurricane season, and voluntary evacuations were set in motion in hopes of avoiding the massive traffic jams when more than 600,000 tried to escape the city as Ivan drew near before veering east last year.

That sense of wariness was less evident nearby on the high-rolling Mississippi Gulf Coast, where miles of casinos generate billions of dollars a year from Biloxi to the Louisiana border. Emergency officials said they were holding off on asking the casinos to close.

Staff writers Catharine Skipp in Key West and Josh White in Washington contributed to this report.

Haitians ford a river after a bridge collapse in Grand Goaves. The storm is on track to arrive in the U.S. Gulf Coast.