Volunteers and emergency personnel worked through the night from Tuesday to Wednesday to fortify the Polish city of Wroclaw against approaching flood waters, while Hungary opened a dam as the prime minister warned a "crucial period" was approaching.
The worst floods to hit central Europe in at least two decades have left a trail of destruction from Romania to Poland, spreading mud and debris in towns, destroying bridges, submerging cars and leaving authorities and householders with a bill for damages that will run into billions of dollars.
"A lot happened tonight," Polish Prime Minister Donald Tusk told a crisis meeting in Wroclaw. "We will need urgent information... from those places that received high water."
Towns to the south of Wroclaw, such as Lewin Brzeski, have already felt the full force of the floods, forcing residents to wade through the streets in waist-high water or seek refuge on the roofs of the entrances to blocks of flats, Reuters reported.
In Hungary, authorities opened a dam in the country's northwest to channel water from the Lajta river into an emergency reservoir, in a bid to protect the city of Mosonmagyarovar.
The water was allowed to flow onto agricultural land.
In the capital Budapest, the Danube is still expected to peak around or slightly above 8.5 metres, likely on Friday or Saturday.
"Due to heavy rains and floods, the situation is critical all across Central Europe," Hungarian Prime Minister Viktor Orban said in a post on social media platform X late on Tuesday.
"According to the latest forecasts, the crucial period for Hungary will begin tomorrow (Wednesday), so flood protection is going full steam ahead.
Drone footage from Tuesday showed the Hungarian village of Venek, near Gyor in the north of the country, submerged under water.
"I think it's kind of connected to the climate change because it's a sudden flood," said 51 year-old local resident Georg Bercsanyi.
"It was raining for four days in the area, especially around Vienna in Austria. So that's why we have this high water level now."
In the Czech Republic, water levels were mostly receding, but rivers were still peaking in some parts of southern Bohemia.
In the worst-hit areas local residents and emergency services were cleaning up part of the railway line form Prague to Ostrava, which is also on the Vienna-Warsaw route, and was still out of operation, as well as some secondary rail lines and roads.
Finance Minister Zbynek Stanjura said on Tuesday he would like parliament to approve an amendment to the budget to make room for flood relief, even though the cost of the damage is still not known. Stanjura said it could perhaps be in the order of $4 billion.
