SAN JUAN, Puerto Rico — Hurricane watches were issued for parts of Cuba and Mexico on Monday as a cluster of storms located south of the Cayman Islands could strengthen into a major hurricane in upcoming days while moving north toward the U.S., weather forecasters said.

The disturbance could become Hurricane Helene on Wednesday as it approaches the Gulf Coast, according to the National Hurricane Center.

“It could certainly become a major hurricane, which is Category 3,” Brad Reinhart, a senior hurricane specialist at the center, said in a phone interview. “People in the Florida Panhandle and the west coast of Florida certainly need to pay close attention.”

Florida Gov. Ron DeSantis declared a state of emergency in 41 counties on Monday as a result of the expected storm.

Reinhart said that it’s too early to forecast where it might make landfall. He warned “there’s always some potential” for it to strengthen into a Category 4 storm, but added that it might not be the most likely outcome.

He said the disturbance could become a tropical storm by Tuesday, and that tropical storm conditions could affect parts of Florida on Wednesday as it approaches. It could turn into a major hurricane by the time it reaches the northeast Gulf Coast on Thursday.

“It’s a pretty aggressive forecast for intensification over the next few days,” he said. “People need to remain on high alert.”

Very warm sea temperatures are forecast to fuel formation of a tropical storm, which is forecast to quickly strengthen into a hurricane thanks to favorable conditions that include a moist atmosphere, which supports thunderstorm developments, and light upper-level winds at more than 10,000 feet (around 3,000 meters), Reinhart said.

The cluster of storms was located about 110 miles (175 kilometers) south-southwest of Grand Cayman on Monday. It had maximum sustained winds of 30 mph (45 kph) and was moving north at 6 mph (9 kph).

A hurricane watch was in effect for the Cuban province of Pinar del Rio and eastern Mexico from Cabo Catoche to Tulum. A tropical storm warning was in effect for eastern Mexico from Rio Lagartos to Tulum and for the Cuban provinces of Artemisa, Pinar del Rio and the Isle of Youth.

Up to eight inches of rain is forecast for western Cuba and the Cayman Islands with isolated total of some 12 inches (30 centimeters). Up to 4 inches (10 centimeters) of rain is expected for the eastern Yucatán Peninsula, with isolated total of more than 6 inches (15 centimeters) inches.

Heavy rainfall also is forecast for the Southeast U.S. starting on Wednesday, threatening flash and river flooding, according to the National Hurricane Center.

Meanwhile, up to 4 feet (1.2 meters) of storm surge is forecast for parts of Cuba and Mexico.

On Monday, authorities in the Cayman Islands closed schools as forecasters warned of heavy flooding associated with the disturbance, which is due to cut a path between Cuba and Mexico’s Yucatán Peninsula in upcoming days.

Helene would be the eighth named storm of the Atlantic hurricane season which runs from June 1 to Nov. 30.

The National Oceanic and Atmospheric Administration has predicted an above-average Atlantic hurricane season this year because of record-warm ocean temperatures. It forecast 17 to 25 named storms, with four to seven major hurricanes of Category 3 or higher.