Hurricane Melissa intensified into a Category 5 storm on Monday, packing sustained winds of up to 175 mph as it approached Jamaica.
The U.S. National Hurricane Center described the slow-moving hurricane as catastrophic, with its wind span exceeding the length of the island.
Melissa is expected to make landfall late Monday or early Tuesday, potentially becoming the strongest hurricane to hit Jamaica on record.
The storm's sluggish pace over warm Caribbean waters has fueled its growth, forecasting up to 3 feet of rain and prolonged destructive winds.
Prime Minister Andrew Holness ordered mandatory evacuations for southern areas, including Port Royal, and warned of severe damage to infrastructure, farmlands, and homes.
An emergency budget of $33 million has been allocated, surpassing provisions from last year's Hurricane Beryl.
Authorities reported buses ready to transport about 28,000 people under evacuation orders, though some residents hesitated due to looting concerns.
In Cuba, over 500,000 individuals were evacuated from coastal and mountainous regions, with more than 250,000 sheltered near Santiago de Cuba.
The Bahamas ordered evacuations in southern and eastern areas, while Turks and Caicos braced for impacts by Wednesday.
Haiti and the Dominican Republic experienced prior heavy rains from Melissa, resulting in at least four deaths and flooding that displaced thousands in Haiti.
Flights were suspended in southern Haiti, and sailing banned amid the storm's effects.
Jamaica's entire island is under threat, with meteorologists warning of life-threatening storm surges, flooding, and landslides lasting days.
Communities in mountainous areas like Hagley Gap reported impassable roads, leaving residents unable to evacuate.
Forecasters noted Melissa could fluctuate but remain a powerful hurricane through the Bahamas.