Elsewhere in central Europe, communities were beginning to count the cost of devastating floods that have hit Germany, Austria, Switzerland, Hungary, Slovakia, Poland and the Czech Republic.
At least 19 people have died over the past week, and experts say the economic damage in Germany alone could top 11 billion euros ($14.6 billion).
The Danube's crest left Austria on Friday and entered Hungary, where Prime Minister Viktor Orban warned that water levels were above the all-time highs.
"It is now certain that we will face the largest-ever flood on the Danube, so we must be prepared for the worst," Orban said Gyor, a western city on the Danube.
The crest was expected to reach Budapest on Monday, and Mayor Istvan Tarlos said in a worst-case scenario up to 55,000 people may need to be evacuated. But he was confident that only the lowest-lying areas of the city would be exposed to the Danube's surge.
Tarlos said the Danube was expected to rise to around 8.95 meters (31 feet) in the downtown area, while the walls along the river and temporary defenses would be able to keep out waters up to 9.3 meters (30 feet, 6 inches).
Farther upstream in Hungary, about 900 people had to leave their homes because of the flood.
In neighboring Slovakia, the situation was critical in the border city of Komarno where the Danube was still rising and was expected to do so till Saturday. Rescuers, soldiers and volunteers have been filling sand bags to reinforce protective barriers.
In the Czech Republic, the government's central crisis committee ordered local authorities to leave all flood protection measures in place because meteorologists have forecast possible heavy rains for the next few days and the situation could get worse again.
"The flooding is not over yet," Czech Prime Minister Petr Necas.
In Germany, meanwhile, water levels were stabilizing in the south and east, even as the crest of the Elbe rolled northward.
Authorities said the greatest dangers remained in the Saxony-Anhalt town of Bitterfeld where levees around a lake were threatening to collapse and in Muehlberg in Brandenburg, where 2,000 residents were told to leave their homes.
Authorities in Magdeburg, the state capital of Saxony-Anhalt, reported that water levels in the Elbe were higher than during the record floods the region experienced in 2002. Since then, flood defenses have been significantly upgraded.
The German military said some 11,300 soldiers were helping build sandbag barriers and flying helicopters over flood zones to ensure levees and dams were holding.
A 74-year-old man died after he was hit by a vehicle carrying sandbags in the eastern German town of Wittenberg. Five other flood-related deaths have been recorded in Germany, ten in the Czech Republic, two in Austria and one each in Slovakia and Switzerland.
Karel Janicek in Prague, Czech Republic, and Pablo Gorondi in Budapest, Hungary, contributed to this report.