As many as 15 people had been lost their lives in Derioa, Gorakhpur, Gonda, Barabanki and Kushinagar districts in the nature's fury, reports reaching Lucknow said.
About 1,100 villages were marooned in 20 districts while over 2,200 villages have been affected owing to rise in major rivers.
While army was called out in Barabanki and Gorkahpur district, PAC had been pressed in other flood-affected districts to evacuate people to safety.
Major rivers including Ghaghra, Saryu, Rapti, Kuano, Gurrah, Rohin and Manorama were showing a rising trend and had crossed danger mark at various places inundating hundreds of villages.
Shravasti, Maharajganj, Kushinagar, Gonda, Baharaich, Ballia, Gorakhpur and Barabanki were the worst affected districts, where necessary measures were taken to provide relief to those affected.
The government has announced an ex-gratia relief of Rs 1.5 lakh each to those killed in flood related incidents, official sources said.
Directives have been issued to the district authorities to maintain high alert and keep a strict vigil near the embankments and dams, sources said.