Heavy rain from the outer bands of Hurricane Matthew have drenched Jamaica and Haiti, flooding streets and forcing thousands of residents to emergency shelters as the category four storm approaches.
Two deaths have been reported in Haiti, bringing the total number caused by the giant storm so far to at least four.
Matthew had sustained winds of 140mph as it moved north. The centre of the storm is expected to pass just east of Jamaica and near or over the south-western tip of Haiti early on Tuesday before heading to eastern Cuba.
Meanwhile in the US, the governor of North Carolina declared a state of emergency for 66 counties in central and eastern parts of the state because Matthew is on a course that could take it along the east coast.
US National Hurricane Centre expert Richard Pasch said: "We are looking at a dangerous hurricane that is heading into the vicinity of western Haiti and eastern Cuba.
"People who are impacted by things like flooding and mudslides hopefully would get out and relocate because that's where we have seen loss of life in the past."
In Jamaica, more than 700 people packed into shelters in the eastern parish of St Thomas and the Salvation Army said there were about 200 people at its shelters in Kingston, as it put out a call for mattresses and beds. Many streets are already flooded throughout the country's south east.
But many people still plan to stick it out at home. Local government minister Desmond McKenzie said all but four residents of the Port Royal area near Kingston airport refused to board buses and clear out.
In Haiti, authorities have been going door-to-door in the south coast cities of Les Cayes and Jeremie to make sure people are aware of the storm. At least 1,200 people have been taken to shelters in churches and schools.
In Port-au-Prince, schools were shuttered and residents lined up at petrol stations and cleared out the shelves at supermarkets as a light rain fell in the capital.
At least two fishermen died in rough water churned up by the storm. A boat carrying one of the men capsized early on Monday off the tiny south-western fishing town of Saint Jean du Sud as he was trying to bring his wooden skiff to shore. The body of the other was recovered a short time later off the nearby town of Aquin after he apparently drowned.
There have been two other storm-related deaths: one man died on Friday in Colombia, and a 16-year-old in St Vincent and the Grenadines on September 28 when the system passed through the eastern Caribbean.
Forecasters said the storm is expected to dump as much as 40 inches of rain on some isolated areas of Haiti, raising fears of deadly mudslides and floods in the heavily deforested country where many families live in flimsy houses with corrugated metal roofs.
Matthew is one of the most powerful Atlantic hurricanes in recent history and briefly reached the top classification, category five, becoming the strongest hurricane in the region since Felix in 2007.
The US hurricane centre said the storm appears to be on track to pass east of Florida through the Bahamas, but it is too soon to predict with certainty whether it will threaten any spot on the US east coast.
"Although our track is to the east of Florida, interests there should remain vigilant and we can't rule out the possibility of impacts," Pasch said.
North Carolina governor Pat McCrory declared a state of emergency, telling a news conference the declaration will immediately help farmers clear their fields of crops already affected by heavy rain over the last two weeks.
He said he did not want other crops ruined, so restrictions on truck weights and hours of service were lifted under the emergency declaration to allow farmers to take their harvest to market.
The governor said he did not want farmers to wait until Thursday to begin work if the storm was close to North Carolina.