Hurricane Melissa It strengthened into a major Category 4 hurricane on Sunday, unleashing torrential rains and threatening to cause flash flooding and landslides in the northern Caribbean, the Miami-based National Hurricane Center said.

The center said those impacts could be “life-threatening and catastrophic” for parts of Haiti and Jamaica, especially since Melissa was forecast to further intensify into a Category 5 storm.

The weather agency added that Melissa is likely to reach Jamaica’s southern coast as a major hurricane late Monday or Tuesday morning, and urged island residents to seek shelter immediately.

“I urge Jamaicans to take this weather threat seriously,” said Jamaican Prime Minister Andrew Holness. “Take all measures to protect yourself.”

Melissa could be the most powerful hurricane to ever hit Jamaica, according to CBS News Philadelphia meteorologist Andrew Kozakhe said on saturday.

Melissa was expected to drop torrential rains of up to 30 inches in Jamaica and southern Hispaniola (Haiti and the Dominican Republic), according to the hurricane center. Some areas may see up to 40 inches of rain.

He also warned that extensive damage to infrastructure, power and communications outages and the isolation of communities were to be expected in Jamaica.

Melissa should be near or over Cuba by Tuesday night, where it could bring up to 12 inches of rain, before moving toward the Bahamas later Wednesday.

The Cuban government issued a hurricane warning on Saturday afternoon for the provinces of Granma, Santiago de Cuba, Guantánamo and Holguín.

At least 4 dead in Hispaniola

The erratic, slow-moving storm has killed at least three people in Haiti and a fourth in the Dominican Republic, where another person remains missing.

“Unfortunately for places along the projected path of this storm, it’s getting more dire,” Jamie Rhome, deputy director of the hurricane center, said earlier Saturday. He said the storm will continue to move slowly for up to four days.

Jamaican authorities said Saturday that Norman Manley International Airport in Kingston will be closed at 8 p.m. local time. He did not say whether he would close Sangster Airport in Montego Bay, on the western side of the island.

In Jamaica, more than 650 shelters were activated. Officials said warehouses across the island were well stocked and thousands of food packages were prepared for rapid distribution if necessary.

Damaged houses, rising water

Haitian authorities said three people had died as a result of the hurricane and five others were injured due to the collapse of a wall. There were also reports of rising river levels, flooding and the destruction of a bridge due to river banks breaking in Sainte-Suzanne in the northeast.

“The storm is causing a lot of concern because of the way it is moving,” said Ronald Délice, director of Haiti’s civil protection department, as local authorities organized lines to distribute food kits. Many residents are still reluctant to leave their homes.

The storm has damaged nearly 200 homes in the Dominican Republic and has left water supply systems out of service, affecting more than half a million customers. It also downed trees and traffic lights, triggered a pair of small landslides and left more than two dozen communities isolated by flooding.

The Bahamas Department of Meteorology said Melissa could bring tropical storm or hurricane conditions to the southeastern and central islands of the Bahamas and the Turks and Caicos Islands early next week.

Melissa is the 13th named storm of the Atlantic hurricane season, which runs from June 1 to November 30.

The U.S. National Oceanic and Atmospheric Administration had forecast an above-normal season with between 13 and 18 named storms.