The Sudanese Government and the UN have launched an appeal to raise $20m (£9.9m) to help more than 400,000 people hit by floods across Sudan.
The floods are said to be the worst in living memory
The UN says at least three-and-a-half million could be at risk from water-borne diseases such as cholera.
Sudanese officials described the floods as the worst in living memory, with heavy rains killing at least 89 people and destroying 73,000 homes.
Experts say they believe there will be more floods over the next few weeks.
A further quarter of a million people could be affected in at least 12 states including Red Sea state, the Blue Nile and Upper Nile as well as the capital, Khartoum.
The appeal money will be used to provide clean water as well as emergency shelter and food to those who are at risk.
"These funds will enable us to save lives, to assist families who lost everything in gradually restoring their livelihoods, to prevent deadly epidemics, and to help children get back to school," UN Undersecretary-General for Humanitarian Relief John Holmes said in a statement.
The money will go towards 48 projects to be carried out around the country by seven UN agencies.
Money already committed has enabled the UN and its partners to provide clean water to more than a million people and shelter to 200,000 homeless.
About 50 people were killed in a cholera outbreak resulting from the floods in the north-east of the country, the World Health Organization says.