Almost 150 people have died and almost 20 million people have been displaced or marooned in severe flooding across India, Bangladesh and Nepal.
In some areas, the floods are being called the worst in living memory.
A vast area is under water, damaging farmland and affecting thousands of villages. Aid agencies say stocks of food and water are running very low.
It has been raining heavily in the region for 20 days and more rain is forecast, particularly in central India, a region which has so far received a weaker monsoon.
Flood politics
Many of the rivers which flow through northern India and into Bangladesh are overflowing, and in some places they have burst their banks.
- 12 million displaced or marooned in India
- 5.5 million displaced in Bangladesh
- More than 750,000 affected in Nepal
In Assam, in north-eastern India, three feet of rain fell in July.
People in the state have clashed with police in their desperation for food, shelter and medicine.
In Uttar Pradesh the army was called in to evacuate 500 villages. The two worst affected districts are reported to be Gorakhpur and Kushinagar, although water levels in major rivers there are reported to have stopped rising for the moment.Bihar's State Disaster Management Committee Chairman Manoj Srivastava told the BBC the flood situation was quite "serious".At least 121 relief camps and 34 cattle camps had been set up in the flood-affected areas of Bihar, he said.
The High Court in the state capital Patna has recently criticised the state government for its failure to deliver relief materials.
Bihar's former chief minister and the current federal railway minister, Laloo Prasad Yadav, made an aerial tour of the region on Wednesday and accused the state government of "criminal negligence".
Chief Minister Nitish Kumar is out of the state on business.
State Governor RS Gavai has appealed to all party leaders to bury their political differences and work together to help flood victims.
Army assistance
Many roads and bridges in the states of Bihar and Assam have been damaged, making it harder for the authorities to get relief material to those affected.
The army is using helicopters to drop supplies but aid agencies are already warning of shortages of food and drinking water.
In Bangladesh, a country that is predominantly low-lying, hundreds of thousands of people are camping on embankments or on the roofs of their homes waiting for relief.
One man who abandoned his home in Sirajganj, 110km (70 miles) north-west of Dhaka, said he and his family had lost everything.
"We are suffering too much here in this makeshift shelter. The flood has destroyed all of our belongings, we could save nothing," he told the BBC.
Many are using boats to move around.
Bangladesh's military-backed interim government has said it is doing its best to cope.
The country's Red Cross says a quarter of a million people have been affected by rains.
There have been deadly landslides in the highlands and floods have hit dozens of districts in the low-lying Terai region.
The weather is improving, but aid workers say the problems for many of the affected people are getting worse.
Some people have blamed India for worsening the situation because it has not opened dams on its side of the border.
But authorities in the Indian state of Uttar Pradesh say the release of flood waters by Nepal causes flooding on their side of the border.