Tropical Storm Helene formed in the Caribbean on Tuesday and could strengthen into a major hurricane as it moves north toward the United States, forecasters said. Heavy rains and high waves have already battered the Cayman Islands, and some Florida residents have been filling sandbags days ahead of expected flooding.

Follow the storm with the live map below.

Hurricane warnings have been issued for parts of Cuba, Mexico and a stretch of coastal Florida, including Tampa Bay, the US National Hurricane Center said. A tropical storm warning has been issued for parts of the Florida Keys.

The storm was located 175 miles south of the western tip of Cuba, had sustained winds of 45 mph (75 kph) and was moving northwest at 12 mph (19 kph). It 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 positioning generators and food and water supplies and deploying search and rescue and power restoration teams, White House spokesman Jeremy Edwards said.

Florida Governor Ron DeSantis declared a state of emergency on Monday before the storm reached the state's Gulf Coast late Thursday, and on Tuesday increased the number of counties declared high-risk from 41 to 61.

“Now is the time to start preparing. If you are in an evacuation zone, you should evacuate,” said Lisa Bucci, a specialist at the hurricane center. “Don't be fooled by what the storm looks like right now.”

The storm is expected to move over deep, warm waters, which will increase its intensity. People in areas under watches and warnings should be prepared for power outages and carry enough food and water to last at least three days, Bucci said.

Helene, the eighth named storm of the Atlantic hurricane season, could strengthen into a Category 3 major hurricane with winds of at least 111 mph (178 kph) before it approaches the northeast Gulf Coast. Since 2000, eight major hurricanes have made landfall in Florida, according to 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, September 24, 2024. Photo by Paola Chiomante/ Reuters

Given the expected size, storm surge, wind and rain will spread far from the center of the expected storm, especially on the east side. Inland states such as Tennessee, Kentucky and Indiana could also expect rainfall related to the storm, Bucci said.

A tropical storm warning was in effect for the Dry Tortugas in Florida, 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 for Grand Cayman was canceled.

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

DeSantis said the storm was reminiscent of Hurricane Michael in 2018, a Category 5 hurricane that rapidly intensified and caught residents by surprise before cutting a devastating swath through the western Florida Panhandle. Communities still rebuilding after previous storms could be hit again, DeSantis warned.

“We are going to see significant impacts no matter what happens,” DeSantis said Tuesday.

The sun was shining in Tarpon Springs, Florida on Tuesday, but residents had already filled sandbags to prepare for possible flooding.

In the Cayman Islands, authorities closed schools, airports and government buildings as strong winds caused power outages in some areas of Grand Cayman and heavy rain and waves up to three metres high caused flooding.

Many people in Cuba are worried about the storm, whose tentacles are expected to reach the capital Havana, which is struggling with severe water shortages, mountains of uncollected garbage cans and constant power outages.

Helene is expected to pass between Cuba and Mexico's Yucatan Peninsula early Wednesday and then move north over the Gulf of Mexico.

Rainfall of up to 20 cm (8 inches) is expected for western Cuba and the Cayman Islands, with isolated amounts as high as 30 cm (12 inches). Rainfall of up to 15 cm (6 inches) is expected for eastern Yucatan, with isolated amounts exceeding 20 cm (8 inches).

Heavy rainfall was also forecast for the southeastern United States starting Wednesday, which could cause flash floods and river flooding, according to the National Hurricane Center. Rainfall of up to 20 centimeters was forecast for the region, and in some places even up to 30 centimeters.

READ MORE: Hurricane John hit the Mexican Pacific coast and killed two people

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

Mexican authorities offered a free ferry service to ferry tourists away 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 such as Cancun, Playa del Carmen and Tulum. Holbox is known among tourists for its calm, shallow waters and flocks of flamingos. It floods easily.

According to Lezama, meteorologists expect the storm to move just off the coast and not reach the Mexican mainland.

The Atlantic hurricane season runs from June 1 to November 30. The National Oceanic and Atmospheric Administration has predicted a stronger than average Atlantic hurricane season this year as the oceans experience record-breaking temperatures. It forecasts 17 to 25 named storms, including four to seven major hurricanes of Category 3 or higher.

In the Pacific, former Hurricane John claimed two lives when it hit Mexico's southern Pacific coast, ripping metal roofs off houses, triggering landslides and downing 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 journalists Andrea Rodríguez in Havana and Mark Stevenson in Mexico City contributed to this report.