TALLAHASSEE, Fla. — An enormous Hurricane Helene swamped parts of Mexico on Wednesday as it churned on a path forecasters said would take it to Florida as a major storm with a surge that could swallow entire homes, a chilling warning that sent residents scrambling for higher ground, closed schools and led to states of emergency throughout the Southeast.

Helene’s center was about 460 miles southwest of Tampa, the U.S. National Hurricane Center said, and the hurricane was expected to intensify and grow as it crosses the Gulf of Mexico.

“Just hope and pray that everybody’s safe,” said Connie Dillard, of Tallahassee, as she shopped at a grocery store with thinning shelves of water and bread in preparation for hitting the highway out of town. “That’s all you can do.”

The hurricane ranks in the 90th percentile for its sheer size, and it could create a storm surge as high as 18 feet in places, forecasters said. The storm’s wind and rain could penetrate far inland, even as it weakens after landfall in Florida late Thursday, authorities warned.

One insurance firm, Gallagher Re, is expecting billions of dollars in damage in the United States.

Around 18,000 linemen from out of state have staged in Florida, ready to help restore power. Federal authorities also have positioned generators, food and water, along with search-and-rescue and power restoration teams.

Airports in St. Petersburg, Tallahassee and Tampa were planning to close Thursday, and 62 hospitals, nursing homes and assisted living facilities evacuated their residents Wednesday.

Helene was moving north at 12 mph with top sustained winds of 85 mph and was expected to intensify over the warm waters of the Gulf.

Forecasters said it should become a Category 3 or higher hurricane Thursday with winds above 110 mph. Its center is projected to hit Florida’s Big Bend area, the curving stretch of Gulf coastline in the state’s north.

In Tallahassee, where stations had started to run out of gas, Florida A&M student Kameron Benjamin, 19, filled sandbags with his roommate to protect their apartment before evacuating. Florida A&M and Florida State shut down.

“This hurricane is heading straight to Tallahassee, so I really don’t know what to expect,” Benjamin said.

As Big Bend residents battened down their homes, many saw the ghost of 2018’s Hurricane Michael. That storm rapidly intensified and crashed ashore as a Category 5 that laid waste to Panama City and parts of the rural Panhandle.

“People are taking heed and hightailing it out of there for higher ground,” said Kristin Korinko, a Tallahassee resident who serves as the commodore of the Shell Point Sailboard Club, on the Gulf Coast about 30 miles south of Tallahassee.

In Crawfordville, Will Glenn spent most of Wednesday boarding up his windows and gathering family mementos before evacuating.

“This could be it,” he said.

For Floridians who are used to hurricanes, Robbie Berg, a national warning coordinator for the hurricane center, warned: “Please do not compare it to other storms you may have experienced over the past year or two.”

With tropical storm-force winds expected to extend for more than 200 miles, Helene is forecast to be one of the largest storms in breadth in seven years to hit the Gulf of Mexico region, according to Colorado State University hurricane researcher Phil Klotzbach.

He said since 1988, only three Gulf of Mexico hurricanes were bigger than Helene is forecasted to reach: Irma in 2017, Wilma in 2005 and Opal in 1995.

“By every measure this makes it worse,” said University of Miami senior hurricane researcher Brian McNoldy. “Places that are not used to experiencing hurricanes are going to experience one.’’

Areas 100 miles north of the Georgia-Florida line can expect hurricane conditions.

And for Atlanta, which is under a tropical storm watch, Helene could be the worst strike on a major Southern inland city in 35 years, said University of Georgia meteorology professor Marshall Shepherd.

“It’s going to be a lot like Hugo in Charlotte,” Shepherd said of the 1989 storm that struck the North Carolina city, knocking out power to 85% of customers as winds gusted above hurricane force.

Landslides were possible in southern Appalachia, with catastrophic flooding predicted in the Carolinas and Georgia, where all three governors declared emergencies. Rainfall is possible as far away as Tennessee, Kentucky and Indiana.

Florida Gov. Ron DeSantis, who already issued an emergency for most counties, warned residents Wednesday that they needed to heed evacuation orders.

In Mexico, parts of the Yucatan Peninsula were under hurricane warnings as Helene wound between it and the western tip of Cuba and into the Gulf of Mexico. The storm formed Tuesday in the Caribbean, and it flooded streets and toppled trees as it passed offshore and brushed the resort city of Cancun.

In Cuba, authorities moved cattle to higher ground and medical brigades went to communities often cut off by storms. The government preventively shut off power in some communities as waves as high as 16 feet slammed Cortes Bay.

In the Cayman Islands, schools remained closed as residents pumped water from flooded homes.

Helene is the eighth named storm of the Atlantic hurricane season, which began June 1.