Tropical Storm Helene formed Tuesday in the Caribbean Sea and could strengthen into a major hurricane as it heads north toward the United States, meteorologists said. Heavy rain and high waves have already battered the Cayman Islands, and some Floridians were filling sandbags days ahead of expected flooding.

Follow the storm with the live map below.

Hurricane warnings were issued for parts of Cuba, Mexico and a stretch of Florida’s coastline, including Tampa Bay, the U.S. National Hurricane Center said. A tropical storm warning was issued for parts of the Florida Keys.

The storm was located 175 miles (280 kilometers) south of the western tip of Cuba, packing sustained winds of 45 mph (75 km/h) and moving northwest at 12 mph (19 km/h). The storm was expected to strengthen into Hurricane Helene on Wednesday as it approached the Gulf Coast and could become a major hurricane on Thursday.

In the U.S., federal authorities are working to deploy generators, food and water, along with search and rescue teams and power restoration teams, White House spokesman Jeremy Edwards said.

Florida Gov. Ron DeSantis declared a state of emergency Monday ahead of the storm’s arrival on the state’s Gulf Coast Thursday night, and expanded the number of counties at risk from 41 to 61 on Tuesday.

“Now is the time to prepare. If you’re in an evacuation zone, you need to evacuate,” said Lisa Bucci, a specialist with the hurricane center. “Don’t be fooled by what the storm looks like right now.”

The storm is expected to move over deep, warm water, fueling its intensification. People in areas under watches and warnings should be prepared for power outages and have enough food and water for at least three days, Bucci said.

Helene, the eighth named storm of the Atlantic hurricane season, could strengthen into a major Category 3 hurricane — with winds of at least 111 mph (178 kph) — before it approaches the northeastern Gulf Coast. Eight major hurricanes have made landfall in Florida since 2000, said Philip Klotzbach, a hurricane researcher at Colorado State University.

Tourists swim on a beach as Tropical Storm Helene approaches the Yucatan Peninsula, in Cancun, Mexico, on September 24, 2024. Photo by Paola Chiomante/Reuters

Given the expected large size, storm surge, wind and rain will extend far from the center of the expected storm, particularly on the eastern side. States as far inland as Tennessee, Kentucky and Indiana could see rainfall associated with the storm, Bucci said.

A tropical storm warning was in effect for Florida’s Dry Tortugas; the lower Florida Keys west of the Seven Mile Bridge; Rio Lagartos to Tulum, Mexico; and the Cuban provinces of Artemisa, Pinar del Rio and the Isle of Youth. A tropical storm warning was lifted for Grand Cayman.

A storm surge warning was in effect for Tampa Bay, Florida, Charlotte Harbor, and from Indian Pass south to Flamingo. A tropical storm warning was issued for the middle Florida Keys from the Seven Mile Bridge to the Channel 5 Bridge; Flamingo to south of Englewood; and from west of Indian Pass to the Walton Bay County line.

DeSantis said the storm is reminiscent of 2018’s Hurricane Michael, a Category 5 hurricane that quickly strengthened and caught residents by surprise before carving a path of destruction through the western Florida Panhandle. Communities still rebuilding from previous storms could be hit again, DeSantis warned.

“We are going to see significant impacts either way,” DeSantis said Tuesday.

The sun was shining in Tarpon Springs, Florida on Tuesday, but residents had already filled sandbags amid fears of possible flooding.

Officials in the Cayman Islands closed schools, airports and government buildings after strong winds caused power outages in parts of Grand Cayman. Heavy rains and waves as high as 10 feet (3 meters) also caused flooding.

Many people in Cuba are worried about the storm, whose tentacles are expected to reach the capital Havana. The city is struggling with severe water shortages, piles of uncollected garbage and chronic power outages.

Helene is expected to pass between Cuba and Mexico’s Yucatan Peninsula on Wednesday morning, then head north across the Gulf of Mexico.

Up to 8 inches (20 centimeters) of rain is forecast for western Cuba and the Cayman Islands, with isolated totals of 12 inches (30 centimeters). Up to 6 inches (15 centimeters) of rain is expected for eastern Yucatan, with isolated totals of more than 8 inches (20 centimeters).

Heavy rainfall was also forecast for the southeastern U.S. starting Wednesday, which could lead to flash flooding and river flooding, the National Hurricane Center said. Up to 8 inches (20 centimeters) of rain was forecast for the region, with isolated totals of 12 inches (30 centimeters).

READ MORE: Hurricane John hit Mexico’s Pacific coast, killing two people

Storm surge of up to 15 feet (5 meters) was forecast from the Ochlockonee River in Florida to the Chassahowitzka, and up to 10 feet (3 meters) from the Chassahowitzka to the Anclote River and from Indian Pass to the Ochlockonee River.

Authorities in Mexico offered free ferry services to take tourists from the low-lying coastal island of Holbox. The offer was made Tuesday by Mara Lezama, the governor of the Caribbean coastal state of Quintana Roo, home to resorts including Cancun, Playa del Carmen and Tulum. Holbox is known among tourists for its calm, shallow waters and flocks of flamingos. It can easily flood.

According to Lezama, meteorologists predict the storm will move just offshore and not make landfall in Mexico.

The Atlantic hurricane season runs from June 1 to November 30. The National Oceanic and Atmospheric Administration has forecast an above-average Atlantic hurricane season this year due to record-warm ocean temperatures. Between 17 and 25 named storms were predicted, with four to seven major hurricanes of Category 3 or higher.

In the Pacific Ocean, former Hurricane John killed two people after it slammed into Mexico’s southern Pacific coast, blowing corrugated roofs off homes, triggering mudslides and toppling dozens of trees, authorities said Tuesday.

— Heather Hollingsworth and Danica Coto, Associated Press

Coto reported from San Juan, Puerto Rico, and Hollingsworth from Mission, Kansas. Associated Press reporters Andrea Rodríguez in Havana and Mark Stevenson in Mexico City contributed to this report.