Florida residents picked store shelves clean and long lines formed at gas pumps Wednesday as Hurricane Irma, a Category 5 monster with potentially catastrophic winds of 185 mph, steamed toward the Sunshine State and a possible direct hit on the Miami metropolitan area of nearly 6 million people.

The most powerful hurricane ever recorded in the Atlantic destroyed homes and flooded streets as it roared through a chain of small islands in the northern Caribbean some 1,000 miles from Florida. Forecasters said Irma could strike the Miami area by early Sunday, then rake the entire length of the state's east coast and push into Georgia and the Carolinas.

"This thing is a buzz saw," warned Colorado State University meteorology professor Phil Klotzbach. "I don't see any way out of it."

NEW: Scenes coming in from St. Maarten... pic.twitter.com/6jU9DqvniZ — Brian Shields (@BShieldsWFTV) September 6, 2017

An estimated 25,000 people or more left the Florida Keys after all visitors were ordered to clear out, causing bumper-to-bumper traffic on the single highway that links the chain of low-lying islands to the mainland.

But because of the uncertainty in any forecast this far out, state and local authorities in Miami and Fort Lauderdale held off for the time being on ordering any widespread evacuations there.

Republican Gov. Rick Scott waived tolls on all Florida highways and told people if they were thinking about leaving to "get out now." But in the same breath, he acknowledged that "it's hard to tell people where to go until we know exactly where it will go."

Amid the dire forecasts and the devastating damage done by Hurricane Harvey less than two weeks ago in Houston, some people who usually ride out storms in Florida seemed unwilling to risk it this time.

"Should we leave? A lot of people that I wouldn't expect to leave are leaving. So, it's like, 'Oh, wow!'" said Martie McClain, 66, who lives in the South Florida town of Plantation. Still, she was undecided about going and worried about getting stuck in traffic and running out of gas.

The many construction cranes at sites around South Florida could pose a serious threat if they are toppled.

In Miami, the deputy director of the Building Department, Maurice Pons, said that there about two dozen such cranes in the city alone and that they were built to withstand winds up to 145 mph, but not a Category 5 hurricane.

He said he could "not advise staying in a building next to a construction crane during a major hurricane like Irma."

As people rushed to buy up water and other supplies, board up their homes with plywood and fill up their cars, Scott declared a state of emergency and asked the governors of Alabama and Georgia to waive trucking regulations so gasoline tankers can get fuel into Florida quickly to ease shortages. Scott said he anticipates gas stations being restocked by Thursday morning and urged people to take only what they need when fueling up.

It has been almost 25 years since Florida took a hit from a Category 5 storm. Hurricane Andrew struck just south of Miami in 1992 with winds topping 165 mph (265 kph), killing 65 people and inflicting $26 billion in damage. It was at the time the most expensive natural disaster in U.S. history.

"We'll see what happens," President Donald Trump said in Washington. "It looks like it could be something that could be not good, believe me, not good."

Trump's exclusive Mar-a-Lago resort in Palm Beach — the unofficial Southern White House — sits in the path of the storm.

This is only the second time on Earth since satellites started tracking storms about 40 years ago that one maintained 185 mph winds for more than 24 hours, Colorado State's Klotzbach said.

University of Miami hurricane researcher Brian McNoldy said Irma could easily prove the costliest storm in U.S. history.

Jeff Masters, director of the Weather Underground forecasting service, warned that high winds and large storm surges will damage expensive properties from Miami to Charleston, South Carolina.

"If it goes right up the Gold Coast like the current models are saying, then the Gold Coast is going to become the Mud Coast," Masters said. "That includes Mar-a-Lago."

While Florida building codes were tightened and enforced more stringently after Andrew, the population since then has grown, coastal development has continued, and climate change has become more pronounced.

Under 2001 rules, housing in most parts of Florida must be built to withstand a Category 3 hurricane, meaning winds of up to 129 mph. Miami-Dade and Broward counties have more stringent building codes requiring some structures to withstand Category 4 winds of 146 mph and 140 mph respectively.

As Irma drew closer, Georgia and South Carolina declared a state of emergency. North Carolina declared a state of emergency taking effect Thursday morning.

"It's just scary, you know? We want to get to higher ground. Never had a Cat 5, never experienced it," said Michelle Reynolds, who was leaving the Keys as people filled gas cans and workers covered fuel pumps with "out of service" sleeves.