Authorities in the United States on Wednesday upgraded Hurricane Michael to an “extremely dangerous” category 4 storm hours before it was to hit the coast of Florida. An advisory from the National Hurricane Center, issued at 2.30 pm Indian time, warned that the storm will produce a life-threatening storm surge and heavy rain along the northeastern Gulf coast.

Hurricane Michael is due to make landfall in Florida near Panama City beach around noon local time, or 9.30 pm India time, on Wednesday, reported the BBC. Along with Alabama and Georgia, Florida has declared a state of emergency and more than 370,000 people have been ordered to evacuate and move to higher ground. More than 483 km of coastline is under threat, said the National Weather Service.

Before moving to the US, Hurricane Michael wreaked havoc in the Caribbean, killing 13 people in El Salvador, Honduras and Nicaragua, reported AP.

Florida Governor Rick Scott on Tuesday described the storm as a “serious and life-threatening situation” and urged people not to take any chances. “If you have been told to evacuate, leave,” he said, asking people to listen to local authorities and move inland to safety.

President Donald Trump also said it was “imperative” for residents to “heed the directions of your state and local officials”.

Hurricane Michael could cause ocean waters to rise by up to nearly four metres in the hardest-hit areas, potentially flooding roads, homes and businesses, reported The Washington Post. Law enforcement and agency teams were on standby to respond as soon as the storm passes and 2,500 Florida National Guard troops were on duty, said Scott. Schools and state offices in the area are to remain shut this week.

“A potentially catastrophic event is developing,” said the forecast office of the National Weather Service serving Tallahassee and surrounding areas. It warned of “widespread power outages, downed trees blocking access to roads and endangering individuals, structural damage to homes and businesses, isolated flash flooding and the potential for a few tornadoes”.

Hurricane Michael is expected to weaken after landfall as it moves across the south-eastern parts of the country, said the National Hurricane Center advisory.

Heavy rain is also expected in North and South Carolina by Wednesday night and Thursday. Last month, at least 11 persons died after Hurricane Florence devastated the two states, causing torrential rainfall and heavy inland flooding.