The late-season storm has killed at least three people in Panama. Meteorologists also predicted it would be the first hurricane to make landfall in Costa Rica in 50 years.
Although it was the tail end of hurricane season, tropical storm Otto reached hurricane strength on Wednesday as it turned toward Central America.
Officials in Panama said three of its citizens had been killed, at least two in mudslides caused by the pounding rain and wind speeds of 120 kilometers per hour, AP reported.
The US-based National Hurricane Center warned that the late-season tempest "will likely result in life-threatening flash floods and mudslides", and cautioned anyone living on the Atlantic coast of Central America that "life-threatening surf and rip-current conditions", should be expected.
The meteorological experts said that they expect the storm to gather strength across the Caribbean, possibly coming ashore in Costa Rica and Nicaragua on Thursday. Should that be the case, it would be the first hurricane to make landfall in Costa Rica since reliable records began being kept in 1951.
Costa Rican authorities said they had evacuated around 4,000 people from coastal regions and near rivers in danger of overflowing.
"We will not allow people to remain in at-risk areas and loss of human life," said President Luis Guillermo Solis, who also warned about its impact on the country's key export of coffee.
Panama closed its schools and government buildings on Wednesday, while Nicaragua ordered evacuations and requested all of its civilian vessels at sea to return to port immediately.
This could be the worst storm the Caribbean has seen since Hurricane Matthew killed 546 people in Haiti in October.
Add new comment
Read our comment policy before posting your viewpoints