Serbia and Bosnia have called for international help to rescue people from inundated areas after the worst flooding since modern records began.
At least 35 people have died and more casualties are expected. Tens of thousands of people have fled their homes.
Waters are now beginning to recede, but officials say dangers remain, the BBC reports. They say the threat of landslides, river surges and the difficulties caused by unexploded land mines in Bosnia remain. The floods are also affecting Croatia.
Officials say that three months' worth of rain has fallen on the Balkans in recent days, producing the worst floods since rainfall measurements began 120 years ago.
A large international aid operation is underway, with rescue helicopters from the European Union, the United States and Russia evacuating people from affected areas.
But Serbian Prime Minister Aleksandar Vucic said his country now needed further help, particularly deliveries of food, clothing and bottled water.
Mr Vucic said emergency personnel and volunteers are preparing for a "flood-wave" on one of the country's main rivers - the Sava.
Ahmed Pjano is a regional director of programmes for the charity Save the Children in Serbia and Bosnia and said frequent landslides are hampering rescue efforts.
Serbia's main power plant in Obrenovac is still at risk. Flooding has already cut total power generation at the Nikola Tesla plant by 40 percent.