On Friday, some areas of the capital, Santo Domingo, saw twice the monthly average rainfall in one day.
Meteorologists said that while they had been aware of heavy rains approaching, they had been surprised by the strength of the sudden downpour.
Poor drainage meant that the water accumulated quickly, turning streets into quick-flowing torrents.
In some parts of Santo Domingo, 232mm (9.1in) of rain fell in a matter of hours, twice the estimate for the month, Weather Bureau Director Gloria Ceballos said.
View of a car dragged by the current in the Los Ríos neighbourhood flooded by the rains, in Santo Domingo, Dominican Republic, 05 November 2022.
Several people are still missing. Of the six people who died, two drowned, two were electrocuted and two were crushed by collapsing walls.
Hundreds of homes have been damaged and the agricultural sector has also been hard hit.
President Luis Abinader said an estimate of the damages would be released on Tuesday.
He added that poor drainage had compounded the flooding in the capital: "It's a problem that continued to grow, the city and greater Santo Domingo area grew without a real drainage system."
Rivers broke their banks as water levels rose