Hurricane Matthew strengthened back to a Category 4 storm as it headed for the US mainland, the the National Hurricane Center reported. Wind speeds were estimated to be at 140 mph and could get stronger.

The powerful storm prompted US President Barack Obama to declare a state of emergency for Florida on Thursday afternoon, allowing federal aid to reach affected areas quicker.

Florida Governor Rick Scott strongly warned people in the path of the storm to evacuate. “You need to leave. Evacuate, evacuate, evacuate.”

Scott spoke in no uncertain terms about the threat the hurricane represented. "Do not go on the beach. This will kill you."

The number of people living in areas that need to be evacuated is estimated to be between 1.5 to 2 million people.

Much of Florida is shutting down in preparation for the hurricane. More than 1,500 flights were cancelled nationwide and the popular Walt Disney World Resort, along with its competitors, Universal Studios and SeaWorld, were shutting down their parks.

2,500 National Guard troops have been activated in Florida to deal with the storm and its aftermath.

Hurricane Matthew has already been blamed for well over 100 deaths in Haiti.