By Mark Dummett
BBC News, Bangladesh
This is an anxious time for the people of Char Atra, an island of silt, sand, paddy fields and huts in the middle of the Ganges.
The monsoon is drenching South Asia, and millions of gallons of water are heading towards the Char from as far away as the Himalayas.
By the end of August, the region will be completely inundated. Instead of walking to school or the market, the 10,000 inhabitants may instead have to swim or move about on banana-tree rafts.
Last minute work is now being done to get things ready; the river is too powerful and the island too low to prevent the floods, but homes and paths can be heightened.
A lot of this work has been sponsored by charity Oxfam and carried out by its local partner, the Shariatpur Development Society.
Hasina Begum's tin-sheet and thatch home has been dismantled and a dozen women are piling up sand so that its base can be raised.
People may be raising their homes but not their hopes for the long term
She says she is relieved because during last year's floods, there was so much water in her hut that she had to tie her children to their bed at night to stop them from rolling off and drowning.
Now she will only have to do that if there is a freak flood, a one-in-50-year event. If this does happen then she can build a platform under the roof and sleep there.
Raising her home to a safe level is simple and cheap work, but Hasina, like most islanders, is too poor to be able to pay for it herself.
In the aid-workers' jargon, they are the "hardcore poor" because they do not own anything and because of their intense vulnerability to the weather conditions and the river level.
Their homes are literally built on sand, and the fact is that one year soon, Char Atra, and everything on it, will be washed away in the floods.
I met one old man there - a veteran of the river - who had been forced to move 22 times in his life as each of his homes was destroyed in turn.
The islanders have learned that the floods are too powerful to be tamed
Then there is the government school. It is by the far the largest and strongest building on the island. It doubles as a shelter for hundreds of families during floods and cyclones.
Its headmaster, Mohammed Abdur Rashid, says it has been rebuilt eight times since he was a pupil.
He says that his best students all dream of leaving the island, and getting a job in a big city like Dhaka, Bangladesh's capital.
Others hope to migrate, as many families in the area have relatives working in Italy.
Only a small fraction attend school. Despite government attempts to introduce family planning, there are lots of children on the island. It is impossible to imagine where they are all supposed to live.
They will face many of the same problems their grandparents encountered: floods, riverbank erosion and hunger.
For sure, they will receive more help from the government and aid agencies, but they also face a new set of challenges.
Because it is such a low-lying and heavily populated country, Bangladesh is one of the countries most exposed to climate change and faces a series of threats:
• By the middle of the century, sea level rises are predicted to wipe out much of its coastal belt, making millions homeless
• The water in the Ganges is already becoming more saline, as sea water reaches further inland
• As a result of its position at the top of the Bay of Bengal, Bangladesh is already one of the countries most prone to tropical storms, and rising sea temperatures could lead to more frequent and more devastating cyclones
• There could be worse floods as the monsoon rains become more erratic, and meltwater from the disappearing Himalayan glaciers hits Bangladesh
• The demise of glaciers could also lead to droughts in the north of the country
The government here is pushing for extra funds from rich carbon-emitting nations so that it can help the people of Char Atra, and elsewhere, adapt to these changes before it is too late.
It, and groups like Oxfam, will be pushing their case later this year when leaders meet in Copenhagen to thrash out a new global deal on climate change.
BBC News will return to Char Atra in a few weeks to see how its residents are coping with the arrival of the monsoon season