Dozens of people have died in Bangladesh and India as a result of monsoon storms and subsequent severe flooding, and millions have had to leave their homes.
Rivers burst their banks within a short time, entire villages had to be evacuated, the authorities announced on Saturday.
According to the weather forecasts, the situation is likely to worsen over the weekend.
According to the authorities, at least 25 people died in Bangladesh alone, including 21 from lightning strikes.
After days of continuous rain, large parts of the north-east of the country are flooded.
In Sylhet, the capital of the hardest-hit region of the same name, the third largest airport in the South Asian country had to cease operations.
More than four million people have been affected by the floods, Sylhet regional government chief Mosharraf Hossain told AFP.
The entire region is without electricity.
A resident of the village of Companyganj described how the place was suddenly completely under water on Friday.
He and his family had to stay on the roof of their house all day until a neighbor rescued them with a makeshift boat.
India was also badly affected
According to the government there, at least 16 people have died since Thursday due to flooding and landslides in the neighboring Indian state of Meghalaya.
At least 18 people died in neighboring Assam;
more than 2.6 million people were affected by the floods.
The state leader, Himanta Biswa Sarma, ordered local authorities to provide all the assistance needed to those affected.
The weather experts predicted new heavy rains for the next two days.
They are likely to further aggravate the situation in northeastern Bangladesh and India's northwest.
Flooding occurs regularly in flat and low-lying Bangladesh.
Just last month, the Sylhet region was hit by the most devastating flood in the past two decades, affecting around four million people.
At least ten people were killed.
According to experts, the number and extent of disasters caused by climate change will continue to increase in the future.