The UN Office for the Coordination for Humanitarian Affairs (OCHA) said on Thursday that the Somali region accounts for 80 per cent of those most affected, including in the South East, Gambela, Oromia, Afar and Sidama regions.
"The floods have caused extensive damage to crops, livestock and vital infrastructure," OCHA added.
"Houses, shops, schools and agricultural lands are submerged. There is also a rise in health risks with increased cases of cholera, malaria and dengue fever."
The humanitarians said many people are still grappling with five consecutive seasons of severe droughts in the Horn of Africa, Xinhua news agency reported.
OCHA said UN Resident and Humanitarian Coordinator Ramiz Alakbarov, Ethiopian officials and United Nations and non-governmental organisation representatives visited flood-affected areas to assess the situation and explore how to scale up relief efforts.
"The United Nations and our partners are supporting the government response and providing food, shelter, water and sanitation, as well as logistics support," the office said.
"In addition to increased logistical capacity, we also need increased funding beyond the immediate humanitarian response to help communities adapt to climate change."
OCHA said this year's Humanitarian Response Plan for Ethiopia, calling for nearly $4 billion, is only one-third funded, at $1.3 billion.
