At least 90 people have died in Nepal and 50 in northeastern India's Assam state over the past week. A dozen have been killed in Bangladesh.
Shiv Kumar, a government official in Assam, said 10 rare one-horned rhinos have died in Kaziranga National Park since the Brahmaputra River burst its banks, flooding the reserve.
Some 4.8 million people spread over 3,700 villages across the state are still affected by the floods, though the frequency of rains has decreased in the past 24 hours, the Assam Disaster Response Authority said. More than 2.5 million have also been hit by flooding in India's Bihar state.
Amid the flooding, 20-year-old Imrana Khatoon delivered her first baby on a boat in floodwaters early Friday while on her way to a hospital in Assam's flooded Gagalmari village, locals said. The woman and the newborn were brought back to their home without getting to the hospital.
Community health worker Parag Jyoti Das, who visited the family, said there were no post-delivery health complications. However, the mother and the child were moved to a hospital on a boat to the nearby town of Jhargaon because of unhygienic conditions due to floodwaters, Das said. The health center in Khatoon's village was flooded and closed.
"I would have felt happier if the baby's father was here," said Khatoon, whose husband works in a hotel in the southern state of Kerala.
More than 147,000 people have taken shelter in 755 government-run camps across Assam, officials said.
Authorities warned they would take action against suppliers who were reported to be distributing poor quality rice and other essentials to marooned people and inmates of temporary shelters at some places.
"We have ordered the arrest of those unscrupulous elements supplying substandard materials and playing with the lives of the affected people," said Himanta Biswa Sarma, Assam's finance minister.
In Nepal, the Home Ministry said about 36,728 families were affected by the monsoon rains. The flooding and mudslides forced some 13,000 families to flee their homes.
In at least two of Nepal's districts, helicopters were used to transport emergency food supplies, while other transport means were being used to move tents and other supplies to the victims.
South Asia's monsoon rains, which hit the region from June to September, are crucial for the rain-fed crops planted during the season.