At its worst today, Dean was expected to produce as much as 20 inches of rain - a deluge which could lead to life-threatening flash floods and mudslides. Sea water could surge over the region's beaches as high as 18ft.
"It is a hugely destructive storm - you don't see Category Five hurricanes every day," said Sky News weather presenter Isobel Lang.
The storm was expected to slash across Belize and the Yucatan, to later emerge in the Gulf of Campeche, where oil production on offshore rigs has been stopped.