In Guatemala, at least 13 people were reported killed with four victims in Nicaragua and one in El Salvador.
Guatemala issued a “red alert” and reported at least a dozen landslides on roads and eight badly damaged bridges.
As rains drenched Central America, Hurricane Jova hit Mexico’s Pacific coast, leaving at least four dead.
Guatemalan President Alvaro Colom said rising water levels in at least 12 rivers were threatening communities.
“I want to send a message to the people to be careful travelling on roads that are likely to collapse and get away from the river banks, because rivers are overflowing,” he said, according to the Guatemala Times.
Mr Colom said four people had been electrocuted in floods and others had been swept away in swollen rivers and in landslides.
Guatemalan forecasters warned the heavy rain would last for another 48 hours. Mountainous areas of the country are particularly vulnerable to mudslides.
Officials in El Salvador said a 19-year-old woman was buried when a wall collapsed under heavy rain.
They said more than 2,000 people had been evacuated from flooded areas and moved to shelters.
In Nicaragua, President Daniel Ortega announced the deaths of four people. Local media said the victims included two children.