Two rivers burst their banks and destroyed a village in the country.
Local politicians and residents said the El Duey and Haina rivers swelled after days of rain, leaving at least 100 people missing, and made dozens of families homeless in Villa Altagracia, about 42km outside Santo Domingo, the Dominican capital.
Survivors said most of the 200 houses in the area were swept away.
"There were a lot of dead," said Luis Melo, a local resident.
Marino Mendoza, another resident, said he had seen up to 30 bodies strewn along the banks of the river.
Thousands of people have been evacuated but no casualties have been reported in Cuba, which has one of the most effective civil protection operations in the region.
The 14th storm of the 2007 Atlantic storm season was not expected to strengthen into a hurricane over water, US National Hurricane Centre forecasters have said.
Forecasters have predicted the storm will veer northeast over the Bahamas on Thursday, away from Florida and clear of oil industry installations in the Gulf of Mexico.
In Haiti, Alta Jean-Baptiste, the national civil protection office director, said that at least 24 people died.
The fatalities included a 14-year-old girl and her mother, killed when an uprooted tree crushed their house in the capital Port-au-Prince.
The country is the most vulnerable of the Caribbean islands to flash flooding and mudslides because most of its trees have been chopped down to make charcoal.
About 3,400 people were staying in emergency shelters and around 400 houses had been destroyed.
Jacques-Edouard Alexis, the Haitian prime minister, said that $1.5 million had been set aside to assist storm victims.