Thousands of people are without shelter in 10 flooded districts, and local officials on Monday distributed rice and lentils and cooking pots to people who lost their homes. The area is mainly farmland where the poor live in mud and straw huts that wash away easily.
At least 100 people have died in Nepal and 84 in neighboring India since Thursday due to torrential rains, authorities said.
The situation in the northern Indian state of Uttar Pradesh worsened after dams were opened in Nepal, said Alok Ranjan, a top official in Uttar Pradesh. Along with incessant rain, the rising waters caused several rivers to breach their banks, he said.
Officials in the state reported 10 more deaths overnight, pushing its toll to 34 over the past three days.
Also in northern India, at least 50 people have died in Uttarakhand state, many of them washed away as rivers overflowed, submerging villages and fields.
People in the worst-affected villages were being evacuated to relief camps set up in government and school buildings, Ranjan said.
State authorities said paramilitary soldiers in about 400 boats were helping to evacuate people from their homes after entire villages were marooned in northern Uttar Pradesh.
Vinod Kumar, a resident of Karonda village in Uttar Pradesh, said flood waters moved in so swiftly that they barely were able to escape.
"Late Friday we saw the water level of the Saryu River rising and by Saturday it had inundated our homes. We left the house with whatever we could manage," Kumar said.
Schools and government buildings were hastily turned into makeshift relief camps, and officials were struggling to provide food and other necessities to thousands of people in the camps, said an official who spoke on condition of anonymity because he was not authorized to speak to the media.
In the remote northeastern Indian state of Assam, flood waters submerged large swathes of Kaziranga National Park, a wildlife reserve, forcing animals to cross a highway to escape to higher ground, said M.K. Yadava, the park's director.
The Kaziranga reserve is home to more than 2,500 of the 3,000 one-horn rhinos left in the wild.
"Some parts of the park are under five feet of flood water from the Brahmaputra River which flows along one side of the park," Yadava said.
Nepal Prime Minister Sushil Koirala appealed to domestic and foreign agencies to help flood victims. The main opposition party, the Communist Party of Nepal-Maoist, disrupted parliamentary proceedings and demanded that the government declare a national emergency.
Dhakal said the government was trying to send medical teams and supplies to prevent diseases such as cholera that can follow flooding. It was also distributing tents and plastic sheets to make temporary shelters, utensils to cook food, and clothes for those who lost their belongings.
The June-September monsoon season often brings flooding to Nepal and India. The rains caused a landslide earlier this month that covered an entire village near Katmandu, killing 156 people.
Last year, more than 6,000 people were killed as floods and landslides swept through Uttarakhand state during the monsoon season. Heavy deforestation over the last few decades has made the area more vulnerable to landslides.