Flood water from the Nile River has devastated villages in Sudan's east, south east and around Khartoum, the capital, over the last few weeks.
Rains, flash floods and overflowing rivers forced hundreds of families to move to main roads, often the highest ground around, as they watched houses and possessions get washed away.
Appeal for aid
The International Federation of Red Cross and Red Crescent Societies said in a statement from Geneva the floods could affect about 2.4 million people across 16 of Sudan's 26 states.
"With the season expected to run until mid-October, meteorological organisations in the region are predicting that as many as 2.4 million people across 16 states could be affected," the organisation said.
The Red Cross appealed for $1.75 million to help some 40,000 Sudanese whose homes have been destroyed in flash floods.
Each year, from around June to September, the rainy season causes floods in Sudan, which is mostly desert at other times of the year.
Last year about 10,000 houses were destroyed during about four months of rains causing the river Nile to burst its banks.
Ali blamed global warming for the worsening rains.
Levels of the Nile in Khartoum last year were higher than in 1988 and 1946 when the worst floods of the last century hit Sudan.