Floods displaced more than 150,000 people in Argentina, Brazil, Uruguay and Paraguay following days of heavy rains blamed on El Niño.
In Paraguay, the hardest-hit nation, more than 130,000 people were evacuated. In Alberdi city, residents fled as walls holding back water appeared on the verge of collapse, authorities said.
Argentina had 20,000 evacuees, half of them from Concordia city, which President Mauricio Macri will visit Sunday.
At least 38 cities were inundated in Brazil, authorities said, with Rio Grande do Sul state the most affected by the flooding.
Uruguay had at least 9,000 evacuees, mostly in Salto.
El Niño is a warming of the eastern Pacific Ocean, which affects global climate fluctuations. The phenomenon is especially strong this year, and may lead to the worst El Niño effects in 15 years, scientists say.