Several people have died in the Caribbean as a result of the storm
A million people on the South Carolina coast are set to be evacuated as Hurricane Matthew heads towards the US.
The state's governor Nikki Haley says the mass evacuation order is expected to be issued on Wednesday afternoon unless there is a major change in the hurricane's path.
Matthew has already wreaked destruction further south in the Caribbean where several people have died.
The Category 4 storm caused major damage after it slammed into Haiti's coastline with winds of up to 230km/h on Tuesday.
The worst Caribbean storm in nearly a decade first hit the southwest of the impoverished island, pounding a largely rural corner with devastating winds, torrential rain and massive waves.
Some residents in shanty towns had been evacuated to shelters but many refused, fearing their already limited possessions may be stolen.
A lot of houses in the south have been destroyed or damaged, according to officials.
And the peninsula has been cut off from the rest of the country after the La Digue Bridge which links the capital Port-au-Prince to the region collapsed.
A man who was too unwell to leave his home to move to a shelter died as the storm crashed though his property in the beach town of Port Salut.
Rising sea levels caused extensive flooding, with some water levels reportedly at shoulder height in Les Cayes as the storm headed north towards Cuba and the Bahamas.
In Haiti, schools and two airports have been closed until Wednesday with more than 500 people evacuated from the city of Jeremie.
The hemisphere's poorest country was already badly affected by a hurricane which hit earlier in the season.
The Red Cross has called for volunteers in South Carolina, where the hurricane is expected to strike by the weekend.
It would be the first major evacuation since Hurricane Floyd in 1999.
Florida governor Rick Scott has urged residents along the Atlantic Coast to prepare for a direct hit, possibly by Thursday night.
And US President Barack Obama has postponed a Hillary Clinton campaign event in the Sunshine State the day before.
At the weekend the hurricane caused the death of another Haitian, a fisherman in St Jean Du Sud in the south, who was killed in heavy seas as the storm approached.
A man died in Colombia and a teenager was killed in St Vincent and the Grenadines as the storm moved through the Caribbean.
Irish aid agency Concern has 128 staff based across Haiti and has stockpiled urgent supplies for communities in need as the storm hits.
Speaking from the capital Port-au-Prince, Concern Worldwide country director Nellie Kingston said there was "an incredible amount” of apprehension in a country where thousands still live in camps six years after a devastating earthquake that killed over 300,000 people and left over 1.5 million people homeless.
“We have many life-saving items such as blankets, shelter equipment and aqua tablets because once the hurricane hits things like electricity and water supplies very quickly become compromised,” she said.
“People have just come through the most horrific earthquake in recent memory. They have been hit by cholera epidemics and now we are facing this.”
“The people of Haiti are amazingly resilient, but there is a feeling of: 'Why us?'”