Tropical Storm Idalia, forecast to land in the southeastern United States as the first major hurricane of the 2023 Atlantic season, moved closer to the Gulf Coast of Florida early Tuesday, forcing evacuations and rushed preparations across the state’s storm-scarred peninsula.

With memories still fresh of Hurricane Ian, the Category 4 storm that thrashed Southwestern Florida last September and killed 150 people, residents dashed to grocery stores and gas stations and readied their homes for Idalia, expected to hit on Wednesday with winds of up to 120 miles per hour.

“Don’t be complacent. Don’t get relaxed,” Mayor Dan Allers of Fort Myers Beach warned residents during a news conference on Monday. The town, situated on Estero Island south of Tampa, bears bomb-like scars from Ian, which made landfall 11 months ago today.

Idalia’s track, which the National Hurricane Center predicts will run parallel to Florida’s western coast for much of Tuesday, made it difficult to predict where the storm would come ashore: a little wobble to the east or the west could move the storm’s center from the less-populated region known as the Big Bend toward Tallahassee to the north or Tampa to the south.

“Almost every time they’ve updated this over the last couple of days, they’ve said it’s going to get stronger,” Gov. Ron DeSantis said. “So buckle up.”

He deployed 5,500 members of the National Guard and said that while emergency utility crews would be ready to fix power lines after the storm, residents across a wide swath of the state should expect to lose electricity.

On Monday, Idalia (pronounced ee-DAL-ya) drenched western Cuba, prompting evacuations in low-lying areas. Forecasters said it would become a hurricane on Tuesday morning as it moved into the Gulf of Mexico, where it could be fueled by abnormally warm waters and “strengthen rapidly” until it makes landfall as a potential Category 3 storm.

Another storm, Hurricane Franklin, also strengthened in the Atlantic on Monday, but it was not expected to pose a serious threat to land.

Forecasters said that Idalia could cause eight to 12 feet of storm surge in the Big Bend, a region loosely defined as the area where the north-south portion of the Florida peninsula curves toward the east-west portion of the Panhandle.

In Cedar Key, a conglomeration of tiny islands connected by small bridges in Levy County, about 100 miles up the coast from Tampa, City Commissioner Sue Colson said people who did not want to heed evacuation orders had to prepare for the possibility that the only road in and out of town could be washed out, or that Cedar Key’s 700 homes could be without power, water and sewer service for weeks.

“We’re three miles in the Gulf,” she said. “We’ve already been experiencing the tides that come from global warming. We have flooding issues pretty regularly.”

The Big Bend was last hit by Hurricane Hermine, a Category 1 storm, in 2016. The damage was limited, given the small population in the area. One person died. Older storms were far deadlier. A rare winter storm on March 13, 1993, brought rushing Gulf waters into people’s homes. Forty-seven people died, many by drowning. And a deadly 1896 storm known as the Cedar Key Hurricane killed at least 70 people in Florida.

In the warm waters of the Gulf, which set temperature records this summer, forecasters expect Idalia to undergo a process known as rapid intensification on Tuesday. The state’s Gulf Coast suffered extensive damage from two other recent storms, Hurricane Ian last year and Hurricane Michael in 2018, that rapidly intensified before striking as major hurricanes, with significant wind speeds and storm surges.

Scientists have shown that hurricanes are likely becoming more powerful because of climate change. And in a warming world, the air can hold more moisture, which means a storm can produce more rainfall, like Hurricane Harvey did in Texas in 2017, when some areas received more than 40 inches of rain in less than 48 hours.

President Biden spoke with Governor DeSantis on Monday and approved an emergency declaration for 46 of Florida’s 67 counties ahead of Idalia’s arrival, as warnings about storm surge and hurricane or tropical storm conditions stretched from south of Tampa to the Alabama border.

As the storm neared, county after county in western and central Florida ordered evacuations of residents in mobile homes and low-lying areas, and officials opened shelters and closed schools. As far as Jacksonville, in the northeast corner of the state, local officials said they feared that serious rainfall could crest rivers and lead to flooding.

Even if the storm does not directly hit Tampa, which has long been experts’ worst-case scenario along Florida’s Gulf Coast, storm surge during a high tide could be destructive. Between four and seven feet of surge were forecast on Monday for the Tampa Bay area.

“There is a cost to living in a beautiful environment,” said Cynthia Silvestri, 79, a resident of St. Petersburg, south of Tampa, who was planning to leave her home on Tuesday, after finding a handyman to help her and her husband put up storm shutters.

Anticipating major disruptions, Tampa International Airport and St. Pete-Clearwater International Airport said they would close on Tuesday, prompting travelers to scramble to change their flights or make other arrangements.

Beverly Cartenuto’s son Albert had his flight into Tampa canceled, and he was rebooked to Orlando, a drive of more than two hours from the family’s home near Sarasota, Ms. Cartenuto said.

Her son had left his car at the Tampa airport when he flew out. “Hopefully he parked on a high floor,” she said.

Reporting was contributed by Camila Acosta, Jennifer Reed, Rebecca Carballo, Christine Chung, Orlando Mayorquin, Claire Moses, Nicholas Nehamas and John Yoon. Kitty Bennett contributed research.