Floods and landslides caused by monsoon rain have killed at least five people and forced around 48,000 people to flee their homes in Myanmar, the relief ministry said.
The Myanmar weather bureau said the Bago River in the south had risen a foot higher on Saturday but was expected to start going down over the coming days.
Some Bago residents evacuated early on Friday while others were caught off guard by the rapidly rising water.
"There are floods every year in Bago but this one is the worst. Normally, the water is around knee- or thigh-deep during the rainy season," Bago resident Soe Min Aung, 23, told AFP, adding that his family had scrambled to buy a boat.
"Some families moved to a monastery but others stayed because they didn't think the water would be too high. In some quarters, the water level is higher than two times my height."
More than 870 people were crammed into a Bago monastery on Friday night and were receiving donated supplies as well as food from monks.
Footage from the southwestern state of Rakhine, which was ravaged in May by Cyclone Mocha, showed large areas of villages and farmland submerged by murky, yellow-brown waters.
Myanmar experiences heavy monsoon rains every year, but scientists believe extreme weather events are being exacerbated by climate change.
Nine states and regions affected
The United Nations Office for the Coordination of Humanitarian Affairs estimated around 50,000 Myanmar people had been affected by heavy monsoon rainfall and rising rivers and creeks since the beginning of August.
"There has been major damage to monsoon paddy crops in Mon and Kayin (states)," the agency said in a statement, adding that water levels in the Bago, Bilin and Salween rivers were now receding.
Flooding began in late July and has affected nine of the country's states and regions, including Rakhine, Kachin, Karen, Mon and Chin.
In Karen state, a landslide cut off an important highway to a town on the border with Thailand, with the country's ruling junta saying it could take a month to build a temporary bridge.
Myanmar is in the grip of a bloody civil conflict between the junta, which seized power in a February 2021 coup, and civilian militias opposed to its rule.
According to a local monitoring group, more than 3,800 people have been killed since the coup, a figure the junta puts at 5,000.
The United Nations sharply criticised the junta for its handling of the aftermath of Cyclone Mocha, which killed at least 148 people and destroyed many homes.
It condemned authorities' refusal to allow aid workers to access the region, prompting state media to accuse the world body of "arrogance, ignorance and self-interest".