KINGSTON, Jamaica (Reuters) - Hurricane Matthew, the most powerful cyclone to form over the Atlantic since Hurricane Felix in 2007, churned across the Caribbean on Saturday on a path expected to put it over Jamaica and Haiti on Monday.

Matthew, with winds at about 150 miles per hour (240 kph), could make landfall as a major storm on Jamaica’s southern coast, home to the country’s capital, Kingston, and its only oil refinery.

The hurricane could also affect tourist destinations such as Montego Bay in the north and the southwest coast of flood-prone Haiti was also in harm’s way, forecasters said.

Matthew was about 385 miles (620 km) southeast of Kingston on Saturday afternoon and the U.S. National Hurricane Center ranked it at Category 4 of the five-step Saffir-Simpson scale of hurricane intensity. Earlier it had been ranked at the top Category 5.

“Matthew is expected to produce total rain accumulations of 15 to 25 inches (38-63 cm) over southern Haiti, with possible isolated maximum amounts of 40 inches,” the Miami-based hurricane center said.

The hurricane could rival the destruction caused by Hurricane Gilbert in 1988, but Jamaican Prime Minister Andrew Holness told Reuters in a phone interview that he was cautiously optimistic.

“The impact of the hurricane will probably be similar or greater than Hurricane Gilbert, but our preparedness would be far better and therefore we would be able to mitigate the effects,” Holness said, adding that he expects hits to both the tourism and agriculture sectors.

The Jamaican capital got a preview of what might be in store when the road to the airport temporarily flooded due to unusually high tides. Rain fell and authorities told fishermen to moor in safe harbor until the storm had passed.

“We’re boarding up the windows and we’re moving things in vulnerable areas to safer areas,” said Mary Lowe, owner of Wilks Bay resort near Port Antonio on the northeast coast.

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Disaster coordinators, police and troops are on high alert and shelters are being opened across the island.

Forecasters described Matthew’s movements as erratic on Saturday, but said it would approach Jamaica and southwestern Haiti on Sunday. Haitian officials said storm preparations were focused on the south, which is prone to devastating flooding.

The hurricane was expected to reach Cuba early on Tuesday.

Cuba declared the first stage of an emergency in five eastern provinces. In its second city, Santiago de Cuba, the ruling Communist Party opened shelters and organized volunteer teams to clean storm drains and gather food stocks.

“We have to work intensely,” said Lazaro Exposito Canto of the party central committee, saying in the Granma newspaper that volunteers would go from house to house to warn of the storm.

Cuba has a solid track record of preparing for storms. The last big one to hit was Sandy in 2012, which though weaker than Matthew caused major damage to property and killed 11 people.

JAMAICANS STOCK UP

Many Kingstonians stocked up on water and food on Friday.

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Tenaj Lewis, 41, a doctor buying groceries in Kingston, said Jamaica was much better prepared for hurricanes than when Gilbert struck.

“The country literally shut down for months,” she said.

Since then, hurricanes have brought a few days of power outages but have not been nearly as destructive and many Jamaicans were unflustered.

Jamaican refining company Petrojam’s is expected to shut down its 28,000 barrel per day Kingston facility eight hours before the storm strikes land, said company spokeswoman Latoya Pennant.

Southwest Airlines LUV.N warned that flights to Montego Bay might be disrupted and said customers could reschedule.