Heavy flooding has now affected some 350,000 people across West Africa, United Nations officials say.
At least 32 people have been killed in Ghana and Burkina Faso.
The BBC reports more than 150,000 people in Burkina Faso have fled their homes, mainly in the capital Ouagadougou.
A UN spokeswoman said the amount of rain that fell in Ouagadougou on one day this week was equal to a quarter of the whole country's annual rainfall.
Neighbouring countries Benin, Guinea, Niger and Senegal are also affected.
The United Nations is warning that numbers killed are likely to rise.
Authorities in Burkina Faso say there is a desperate need for blankets, clothes and food and President Blaise Compaore has appealed to the international community for help.
The waters flooded 24,000 homes and the city's infrastructure, washing away roads and cutting electricity.
Two dams have been destroyed and 12 bridges damaged.