A hurricane-force wind gust was recorded in the Florida Keys late Saturday night -- the first sign of deadly Hurricane Irma's impending landfall on the U.S. mainland.
The weather service said the Smith Shoal Light station recorded a 74 mph wind gust on Saturday night, the Associated Press reported.
Meanwhile, the center of Irma was headed toward the Keys with sustained winds of 120 mph.
The edge of Hurricane Irma kicked up surf, whipped up palm trees and spun up at least one confirmed tornado as it approached landfall in Florida Saturday evening.
Irma had been downgraded to a Category 3 storm as it raked the coast of Cuba Saturday morning, but it was expected to get its strength back over the ultra-toasty Florida Straits and hit the peninsula Sunday morning as a dangerous Category 4 storm.
"This is your last chance to make a good decision," Gov. Rick Scott warned residents in Florida's evacuation zones, which encompassed a staggering 6.4 million people, or more than 1 in 4 people in the state.
As of 2 a.m. ET Sunday, the National Hurricane Center (NHC) placed Irma about 70 miles southeast of Key West with winds of up to 130 miles per hour. The center said the storm was moving west-northwest at 6 mph.
President Donald Trump tweeted about Irma shortly before 11 p.m. ET. "The U.S. Coast Guard, FEMA and all Federal and State brave people are ready. Here comes Irma. God bless everyone!," the president wrote.
The National Weather Service in Miami posted on Twitter on Saturday evening that a tornado had touched the ground in the Fort Lauderdale suburb of Oakland Park. It wasn't immediately clear how much damaged was caused.
Tornado warnings have been issued for Fort Lauderdale, Coral Springs, Pompano Beach and Sunrise in Broward County, as well as parts of nearby Palm Beach and Hendry Counties.
More than 75,000 people had lost power by Saturday evening, mostly in and around Miami and Fort Lauderdale, as the wind began gusting.
For days, the forecast had made it look as if the Miami metropolitan area of 6 million people on Florida's Atlantic coast could get hit head-on by the long-dreaded Big One.
But that soon changed. Meteorologists predicted Irma's center would blow ashore Sunday morning in the perilously low-lying Florida Keys, then hug the state's west coast, plowing into the Tampa Bay area by Monday morning.
Still, Miami was not out of danger. Because the storm is 350 to 400 miles wide, the metro area could still get life-threatening hurricane winds and dangerous storm surge of 4 to 6 feet, forecasters warned.
The new course threatens everything from Tampa Bay's bustling twin cities of Tampa and St. Petersburg to Naples' mansion- and yacht-lined canals, Sun City Center's retirement homes, and Sanibel Island's shell-filled beaches.
By late morning Saturday, however, few businesses in St. Petersburg and its barrier islands had put plywood or hurricane shutters on their windows, and some locals grumbled about the change in the forecast.
"For five days, we were told it was going to be on the east coast, and then 24 hours before it hits, we're now told it's coming up the west coast," said Jeff Beerbohm, a 52-year-old entrepreneur in St. Petersburg. "As usual, the weatherman, I don't know why they're paid."
With the new forecast, Pinellas County, home to St. Petersburg, ordered 260,000 people to leave, while Georgia scaled back evacuation orders for some coastal residents.
Tampa has not been struck by a major hurricane since 1921, when its population was about 10,000, National Hurricane Center spokesman Dennis Feltgen said. Now the area has around 3 million people.
Nearly the entire Florida coastline remained under hurricane watches and warnings, and leery residents watched a projected track that could still shift to spare, or savage, parts of the state.
Forecasters warned of storm surge as high as 15 feet.
"This is going to sneak up on people," said Jamie Rhome, head of the hurricane center's storm surge unit.
About 70,000 people crowded into 385 shelters across Florida.
In Key West, 60-year-old Carol Walterson Stroud sought refuge in a senior center with her husband, granddaughter and dog. The streets were nearly empty, shops were boarded up and the wind started to blow.
"Tonight, I'm sweating," she said. "Tonight, I'm scared to death."
At Germain Arena not far from Fort Myers, on Florida's southwestern corner, thousands waited in a snaking line for hours to gain a spot in the hockey venue-turned-shelter.
"We'll never get in," Jamilla Bartley lamented as she stood in the parking lot.
The governor activated all 7,000 members of the Florida National Guard, and 30,000 guardsmen from elsewhere were on standby.
In the Orlando area, Walt Disney World, Universal Studios and Sea World all prepared to close Saturday. The Miami, Fort Lauderdale and Orlando airports shut down, and the Tampa airport planned to do the same later in the day. The Sunshine Skyway Bridge spanning Tampa Bay was closed.
Given its mammoth size and strength and its projected course, it could prove one of the most devastating hurricanes ever to hit Florida and inflict damage on a scale not seen here in 25 years.
Hurricane Andrew razed Miami's suburbs in 1992 with winds topping 165 mph (265 kph), damaging or blowing apart over 125,000 homes. The damage in Florida totaled $26 billion, and at least 40 people died.
Boat captain Ray Scarborough and his girlfriend left their home in Big Pine Key and fled north to stay with relatives in Orlando. Scarborough was 12 when Andrew hit and remembers lying on the floor in a hall as the storm nearly ripped the roof off his house.
"They said this one is going to be bigger than Andrew. When they told me that," he said, "that's all I needed to hear."
The Associated Press contributed to this report.