"Although this is not a hurricane or a tropical storm, the damage observed in the affected areas is extensive," said Jean-Martin Bauer, UN coordinator for humanitarian action in Haiti.
The city of Léogâne, about four miles southwest of the capital Port-au-Prince, is particularly affected as three nearby watercourses have flooded. According to the authorities, 20 people in the city have died.
"The residents are desperate. They have lost everything. The water has destroyed their fields, swept away their livestock," said Léogâne Mayor Ernson Henry.
The high death toll highlights the country's vulnerability to natural disasters and how it has failed to mitigate risks just ahead of this year's hurricane season.
Even before the floods, nearly half of Haiti's population was in need of humanitarian assistance, according to the United Nations.