Tropical Storm Helene is expected to make landfall off Florida’s Gulf Coast late Thursday as a powerful hurricane, forecast to be potentially the strongest storm to hit the United States in over a year.

The storm is expected to strengthen into a Category 3 hurricane as it moves across the Gulf of Mexico.

It moved from the coast of Mexico’s Yucatán Peninsula into the Gulf of Mexico, where it would “rapidly intensify into a major hurricane and increase in size in the eastern Gulf of Mexico, with the threat of life-threatening storm surge along the entire west coast of Florida and the Big Bend region,” the National Hurricane Center said Wednesday morning.

The center, part of a federal agency, said Helene is expected to have greater wind spread than 90 percent of other major hurricanes, with wind fields and rain bands expected to extend more than 140 miles (225 kilometers) east of the eye.

Meteorologists early Wednesday morning predicted the storm would intensify from a 45-mile-per-hour (72-kilometer-per-hour) tropical storm to a Category 3 hurricane in less than 48 hours.

On its current track, the storm’s powerful core could pass directly over Florida’s capital city of Tallahassee. Hurricane and tropical storm warnings have been issued for the state’s west coast, from the Florida Keys and inland to Orlando, as well as most of the east coast and up to the so-called Big Bend coast and the Tallahassee area as the coast then extends west to the Florida Panhandle.

Evacuations of thousands of people south of Tallahassee were underway on Wednesday morning, and on Tuesday afternoon Joe Biden declared a state of emergency for Florida. The US president promised to provide federal resources before the storm arrives.

Florida Governor Ron DeSantis extended the state of emergency to 61 of the state’s 67 counties. Mandatory evacuations are in place in the Big Bend region, where the highest storm surges are expected.

At a press conference Tuesday morning, DeSantis said the state had deployed the Florida National Guard, search and rescue teams and Florida fisheries and wildlife teams to respond. The U.S. Federal Emergency Management Agency has also deployed teams.

“You can hide from the wind,” DeSantis added. “But the water can be very, very devastating if you stay there when you’re told to evacuate.”

Kevin Guthrie, director of the Federal Emergency Management Agency (FEMA), said Helene would be a very large storm even compared to recent storms, warning that it “could be nearly twice the size of Debby and Idalia and potentially have a stronger core.”

Jamie Rhome, deputy director of the Hurricane Center, said: “The wind path of this system will be massive, essentially cutting a path directly across a large portion of the Florida peninsula, including the densely populated I-4 corridor.”

Further north, Georgia Governor Brian Kemp also declared a state of emergency and instructed emergency responders to “prepare and deploy the necessary resources well in advance of the storm’s arrival. Stay alert and stay safe,” he said on X.

The storm’s rapid intensification comes as water temperatures in the Gulf reach 90 degrees. Hurricane forecasters had expected an unusually busy season, but that hasn’t materialized, allowing storm-friendly ocean temperatures to rise without interruption and increase Helene’s power, fueled by the climate crisis that is rapidly warming seas and likely intensifying storms.

When Helene reaches the United States (expected late Thursday or early Friday), it will be the fourth hurricane to make landfall in the United States this year and the fifth to hit Florida since 2022.