Tourist resorts in Mexico's Yucatan Peninsula girded on Thursday for a hit from Hurricane Beryl, which is still packing ferocious winds after slamming Jamaica and the Cayman Islands.

Beryl dropped to a Category 2 storm, with winds of 175 kilometres per hour, and was expected to weaken further as it headed towards landfall overnight on Thursday into Friday on the peninsula, the US National Hurricane Centre (NHC) said.

As of mid-afternoon on Thursday it was in the Caribbean about 445 kilometres east of Tulum, which is about a two-hour drive from Cancun – the two main resort cities in the region.

The storm already left a trail of destruction across the Caribbean and the coast of Venezuela, killing at least seven people.

It is the first hurricane since NHC records began to reach the Category 4 level in June and the earliest to reach the highest Category 5 in July.

In Mexico, classes in the area bracing for a hit were suspended and shelters were set up for locals and tourists.

In Cancun, people have been stocking up on food and other essentials for days and hotels have boarded up their windows.

Beryl is expected to hit the Yucatan Peninsula, emerge over the Gulf of Mexico, then arrive in the northern state of Tamaulipas, which borders the United States.

The hurricane has already caused flash floods and mudslides in the Cayman Islands.

In Jamaica, more than 400,000 people were without power, according to the Jamaica Gleaner newspaper, citing a public service company.

It is extremely rare for such a powerful storm to form this early in the Atlantic hurricane season, which runs from early June to late November.

Warm ocean temperatures are key for hurricanes, and North Atlantic waters are currently between two and five degrees Fahrenheit (1-3 degrees Celsius) warmer than normal, according to the US National Oceanic and Atmospheric Administration (NOAA).

UN climate chief Simon Stiell, who has family on the island of Carriacou, said climate change was "pushing disasters to record-breaking new levels of destruction."

"Disasters on a scale that used to be the stuff of science fiction are becoming meteorological facts, and the climate crisis is the chief culprit," he said on Monday, reporting that his parents' property was damaged. (AFP)