Forecasters say Ernesto has become a hurricane off the coast of Honduras and is headed toward the Yucatan Peninsula.
The U.S. National Hurricane Center said Ernesto had winds of 80 mph and was located about 185 miles east of Chetumal, Mexico.
The center of the storm is expected to make landfall near Mexico's border with Belize later Tuesday or early Wednesday. The storm is expected to bring strong winds and torrential rains to the Caribbean coast.
Soldiers and police were moving 600 residents from the fishing village of Punta Allen in Mexico's Quintana Roo state, where authorities opened emergency shelters and began preparing for the evacuation of other low-lying coastal settlements.
The heart of the storm was expected to hit south of Cancun and the Riviera Maya, though strong rain and winds were likely there.