Massive floods have swept through swathes of India, Nepal and Bangladesh in recent days, killing scores of people and affecting millions of others.
Large-scale rescue operations are under way, with authorities directing thousands to shelters while sending food and supplies to those who are stranded.
Major rivers including the Brahmaputra and the Koshi, which flow through several countries, have overflowed their banks due to heavy rain, reports BBC.
Floods and landslides are not uncommon during South Asia's monsoon season, when it receives up to 90 per cent of its annual rainfall.
But experts say the issue has worsened in recent years due to climate change.
Over the weekend in Nepal, authorities said 14 people had died since Thursday, with key highways blocked and some bridges swept away by swollen rivers.
Authorities estimate that this year's monsoon has killed more than 40 people so far. They have urged residents in the south-east of the country to be on alert as the Koshi river, which flows through Nepal and India, is flowing above the danger level.
"This is not new for us, but the timing is wrong," Kathmandu resident Rajkumar Bk told Reuters news agency.
"The flooding triggered by heavy rains started early this year, in July. The water level has reached up to our knees. If the rainfall continues the same way then we will have to run for our lives."
In the Indian state of Assam, about 2.4 million have been affected by floods while 66 people have died since mid-May. Officials have warned of even more rain with water levels in the Brahmaputra expected to increase in the coming days.
Roads and vast areas of farmland have been submerged along the banks of the Brahmaputra, which flows through parts of India and Bangladesh, and other rivers.
Television pictures in recent days showed villagers salvaging their belongings and leaving their inundated homes by boat. Several bridges and roads have been washed away, disconnecting remote villages.
Assam's Kaziranga nature reserve, home to nearly 2,200 one-horned rhinos, was also under water. Four rhinos and scores of deer and other animals have died so far. Experts have said it is one of the worst incidents of flooding in recent years in terms of the number of animals killed.
On Monday, officials closed some schools in India's financial capital Mumbai as heavy rains overwhelmed some roads.
In Bangladesh, authorities said two million people have been affected by floods with at least eight people dead.
The overflowing Brahmaputra has inundated a quarter of the districts in the country.
"We live with floods here. But this year the water was very high. In three days, the Brahmaputra rose by 6ft to 8ft (2m-2.5m)," Abdul Gafur, a local councillor in the district, told the AFP news agency.
"We are trying to deliver food, especially rice and edible oil. But there is a drinking water crisis."
The UN's World Meteorological Organisation is predicting "above normal" rainfall for the South Asia monsoon season that is expected to last until September.
