NAIROBI, Kenya (CNN) -- Heavy rains triggered by El Nino weather patterns could potentially prove devastating for east African nations that have been water-starved for months, the United Nations has warned.

A Turkana boy holds an empty cup in a village in northwestern Kenya.

Kenya, Somalia, Tanzania and Uganda are facing mudslides, crop destruction, waterborne diseases and disrupted road networks, the U.N. Office for the Coordination of Humanitarian Affairs said Friday. Djibouti, Eritrea and Ethiopia could also be affected.

The effects of flooding are expected to be exacerbated because so much greenery has disappeared in the drought.

"More than 23 million people in pastoral, agricultural and suburban communities, as well as internally displaced people and refugees in the region, are reeling from the impact of water and food shortages, pasture scarcity, conflict and insecurity," said John Holmes, the under-secretary general for humanitarian affairs who is coordinating emergency relief operations.

"While we cannot prevent these climatic shocks, we certainly can mitigate their disastrous effects through forward planning and the right funding from the donor community," he said.

Uganda, hit by El Nino a decade ago, is planning to apply some of the lessons learned this time around, said Fred Opolot, a government spokesman.

"The government has allocated funds and resources to areas that will be affected," he said. "Our disaster preparedness department is using press briefings, among other ways, to inform the public."

Though the department is not very well-funded, he said, the government is working with groups such as the United Nations and international aid agencies to prepare for floods.

"It is a multifaceted effort ... we want to ensure citizens are sensitized to the dangers of El Nino and things such as bridges are in good condition."

The rainy season begins in the Horn of Africa in mid-October and runs through the end of the year. Meteorologists have forecasted that this year's rains will be more intense than usual because of the El Nino phenomenon, caused by a rise in temperature in the Pacific and Indian oceans.

Aid agencies are already buckling under the weight of helping millions of people who have suffered through months of failed crops, drought and erratic rains caused by climate change.

In Somalia, 450,000 people in the Juba and Shabelle river basins could suffer, the United Nations estimates. In neighboring Kenya, some 750,000 people -- 150,000 of whom are refugees -- could be affected.

The Turkana, a pastoral tribe in northeastern Kenya, is already reeling from a severe drought that has left scores of people dead and remains of skeletal cows strewn across the flat, arid land. The remote region has no access to resources, making it especially vulnerable to natural disasters such as floods.

CNN's Moni Basu and Faith Karimi contributed to this report.

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