Friday’s appeal came after torrential rains in the Upper Nile and Bahr el-Ghazal regions.
Information Minister Michael Makuei Lueth said the floods have displaced thousands of people and claimed hundreds of lives.
Earlier this week, President Salva Kiir appealed to humanitarian partners for help.
South Sudan has experienced heavy flooding over the past three years, with more than 800,000 people affected in 2021 alone.
Since the beginning of rainy season in May, flooding in parts of the country has forced some health centers to close and stranded populations, leaving them vulnerable to water-borne diseases and snake bites.
By Deng Machol