Residents of Florida have been stocking up on essential supplies after forecasters said a potentially devastating category 4 hurricane could make land there during a national holiday.

Donald Trump said he was cancelling a trip to Poland in order to oversee the federal response if Hurricane Dorian smacks into the state, where the governor has already declared a state of emergency.

“It's something very important for me to be here,” the president told reporters at the White House. “The storm looks like it could be a very, very big one indeed."

The storm, currently a Category 1 hurricane, was on Thursday night moving northwest at speeds of up to 85mph and was about 330 miles east of the Bahamas, the National National Hurricane Centre said.

It is expected to make landfall somewhere on Florida's east coast on Monday - the Labour Day national holiday - before moving over central Florida the following day. The centre says category 4 storms can cause “catastrophic” damage, and Dorian could have a major impact on the state’s large cities as well as popular tourist destinations.

Tropical storm Dorian expected to strengthen to hurricane Show all 7 1 /7 Tropical storm Dorian expected to strengthen to hurricane Tropical storm Dorian expected to strengthen to hurricane Shoppers preparing for the arrival of tropical storm Dorian stock up on supplies at a supermarket in Bridgetown, Barbados, on 25 August 2019. The US National Hurricane Centre warned the storm was expected to strengthen to a hurricane by the time it reached Puerto Rico on 28 August 2019. REUTERS/Nigel R Browne Tropical storm Dorian expected to strengthen to hurricane Residents board up a pharmacy in Bridgetown, Barbados, 26 August 2019. AP/Chris Brandis Tropical storm Dorian expected to strengthen to hurricane Storm clouds gather as tropical storm Dorian moves towards St Michael Parish, Barbados, 26 August 2019. AP/Chris Brandis Tropical storm Dorian expected to strengthen to hurricane Nearly empty shelves where bottled water is normally displayed at a supermarket in Cabo Rojo, Puerto Rico, 26 August 2019. REUTERS/Ricardo Arduengo Tropical storm Dorian expected to strengthen to hurricane Hotel employees remove sun loungers from a pool area in Gros Islet, St Lucia, 26 August 2019. REUTERS/Andrea de Silva Tropical storm Dorian expected to strengthen to hurricane Empty shelves that are normally filled with bread are seen empty at a supermarket in Gros Islet, St Lucia, 26 August 2019. REUTERS/Andrea de Silva Tropical storm Dorian expected to strengthen to hurricane Tropical storm Dorian is pictured off the coast of Venezuela in this NASA satellite photo, 26 August 2019. NASA/Handout via Reuters

Making the situation tougher for residents, is the fact that with it still four days away from landfall, the possible location for coming ashore stretches over a vast area, reaching from the Florida Keys to southeast Georgia. Governor Ron DeSantis had declared a state of emergency for 26 counties on the east coast but extended it on Thursday to the whole of Florida.

Authorities cancelled some commercial flights, planned precautions at rocket launch sites along the Space Coast and prepared to give out sand to residents for sandbags ahead of the storm's arrival.

“All residents, especially those along the east coast, need to be prepared for possible impacts,” Mr DeSantis said in a statement.

“As it increases strength, this storm has the potential to severely damage homes, businesses and buildings, which is why all Floridians should remain vigilant. Do not wait until it is too late to make a plan.”

US coast guard rescues man and dog from Louisiana before Hurricane Barry hits

Dorian, after sideswiping Caribbean islands without doing major damage, is expected to slam the Bahamas and the southeastern United States with rain, strong winds and life-threatening surf over the next few days.

Jim McKnight, city manager of Cocoa Beach on central Florida's Atlantic coast, made sure construction sites were secured with possible dangers like scaffolding taken down to prevent flying objects.

“We're worried. This is not looking good for us. We woke up a lot more scared than we went to bed last night, and the news is not getting any better,” said Angela Johnson, 39, bar manager at Coconuts On The Beach, a bar and restaurant on the town's surfing beach.

The biggest hurricane to have come ashore in the area in recent history was Jeanne in 2004, which made land around Port St Lucie as a Category 3 storm.

University of Miami hurricane researcher Brian McNoldy said it the storm hit Florida with the force it is currently expected to, it could create major problems.

“If it makes landfall as a Category 3 or 4 hurricane, that's a big deal,” he said.“A lot of people are going to be affected. A lot of insurance claims.”

Along Florida's east coast, local governments began distributing sandbags, shoppers rushed to stock up on food, plywood and other emergency supplies at supermarkets and hardware stores, and motorists topped off their tanks and filled fuel cans. Some fuel shortages were reported in the Cape Canaveral area.