Hurricane Helene forecast to be most powerful storm to hit US in a year

Tropical Storm Helene strengthened into a hurricane on Wednesday morning.

The tempest was labeled a category 1 hurricane and the US National Hurricane Center (NHC) said it was packing maximum sustained winds of 80mph (128km/h) as it churned in the eastern Gulf of Mexico just off the coast of the Yucatán peninsula.

It is expected to hit Florida’s Gulf coast later on Thursday as a forceful hurricane and is forecast to potentially be the most powerful storm to hit the US in more than a year.

The storm will almost certainly continue intensifying throughout the day and into Thursday, when it will bring life-threatening storm surge to much of Florida’s coastline, according to forecasters.

More than 40 million people in Florida, Georgia and Alabama were under hurricane and tropical storm warnings, the National Weather Service said on Wednesday.

Numerous evacuations were being ordered along Florida’s Gulf coast, including Sarasota and Charlotte counties, and dozens of counties have announced school closures, including Hillsborough and Pinellas counties.

The storm could build to a category 3 hurricane as it roars across the Gulf. It threatens “the entire west Florida coast and Big Bend area”, the NHC said on Wednesday morning.

The hurricane center, part of a federal agency, said Helene was expected to have a bigger high-wind expanse than 90% of other major hurricanes, with its wind field and rain bands expected to stretch more than 140 miles east of the eye.

Visual projections showed the huge storm swirling off Cancún, Mexico, with Cuba affected and outer weather effects already reaching eastern Florida.

Forecasters early on Wednesday morning predicted storm intensification from a 45mph tropical storm to a category 3 major hurricane in less than 48 hours.

On Wednesday afternoon, the national hurricane center said the storm was about 480 miles south-west of Tampa, with maximum sustained winds of 80mph.

On its current track, the powerful core of the storm could cross directly over Florida’s state capital 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 through the so-called Big Bend region and the area around Tallahassee, where the coast then stretches west into the Florida Panhandle.

Related: Biden declares emergency as Florida braces for Tropical Storm Helene

Evacuations of thousands of people south of Tallahassee were under way on Wednesday morning and Tuesday afternoon, and Joe Biden declared a state of emergency for Florida. The US president pledged federal resources ahead of the storm hitting.

Some were beginning to talk about the prospect of Helene spinning itself up into a category 4 hurricane, although official reports had not forecast that as of Wednesday midday on the US east coast.

Ron DeSantis, Florida’s governor, expanded a state of emergency to 61 of Florida’s 67 counties and mandatory evacuations are set to begin in the Big Bend area, where the highest storm surges are anticipated.

At a press conference on Tuesday morning, DeSantis said the state had deployed Florida national guard, search and rescue teams, and Florida fish and wildlife crews to respond. The Federal Emergency Management Agency has also deployed teams.

“The wind you can hide from,” DeSantis added. “But it is the water that can be very, very devastating if you remain there when you are told to evacuate.”

Kevin Guthrie, the executive director of Florida’s division of emergency management, said Helene was set to be a very large storm, even compared with recent tempests, warning it could be “nearly twice the size of Debby and Idalia, with possibly a stronger core”.

Jamie Rhome, deputy director of the hurricane center, said: “The wind swath is going to be huge with this system, and it is basically going to carve a path right over a good portion of the Florida peninsula, including the highly populated I-4 corridor.”

Farther north, Georgia’s governor, Brian Kemp, also declared a state of emergency and directed management teams “to prepare for and direct resources well in advance of the storm’s arrival. Stay vigilant and stay safe,” he said on X.

The storm’s rapid intensification comes as water temperatures in the Gulf reach 90F (32C). Hurricane predictors had been expecting an unusually busy season but that has not materialized, allowing storm-friendly sea temperatures to increase without interruption and fuel Helene’s power, driven by the climate crisis that is rapidly warming seas and is believed to intensify storms.

When Helene makes US landfall, expected late on Thursday or early Friday, it will be the fourth hurricane to make landfall in the US this year and the fifth to slam into Florida since 2022.

The Associated Press contributed reporting