Hurricane Helene has rapidly strengthened in the Caribbean Sea while moving north between the coasts of Mexico and Cuba towards the United States, prompting officials to declare an emergency in Florida.

Helene is expected to move over deep, warm waters, fuelling its intensification on Wednesday as it moves north across the Gulf of Mexico, the US National Hurricane Center (NHC) said.

Heavy rainfall was forecast for the southeastern US starting Wednesday, with a “life-threatening storm surge” along the entire west coast of Florida, according to the NHC.