Waters which have battered the south of Poland for the past few days have reached the capital, Warsaw.
Nine people have died in the country's floods this past week and three people are missing.
The latest victim was a 70-year-old man who drowned in his house in Tarnobrzeg, the national rescue service said.
Prime Minister Donald Tusk presented parliament with a report on the floods sparked by torrential rains, saying their scale was 'without precedent in the past 160 years'.
'We're talking about damage worth about 10bn zlotys' (€2.43bn), he said.
'The situation in the River Vistula basin is much worse than in the last major floods of 1997.'
If the cost of flood damage is found to have exceeded €2.1bn, Poland can formally request help from a European Union crisis fund, Mr Tusk's chief aide Michal Boni told parliament. That would unlock €100m of EU money.
At Poland's request, the 27-nation EU formally kicked off an emergency operation on Wednesday.
Among the individual EU member states who have so far sent rescuers and equipment are France, Germany, the Baltic nations of Lithuania, Latvia and Estonia, and Poland's neighbour the Czech Republic, which has also been hit by floods.
Mr Boni said that 23,000 people had been evacuated from flood-hit regions, out of a total affected population of 100,000.
The Vistula winds in an 'S' shape across Poland for 1,050km from the mountainous south to the Baltic Sea in the north.
The swollen river has been bursting its banks at various points along the way, with southern Poland the hardest-hit region so far.
Thousands of people have been evacuated from flood-struck communities, where homes and roads remain submerged.
The water level in Warsaw reached 760cm this afternoon.
Since accurate records began after WWII, the Vistula has only risen above 750cm three times, in 1947, 1960 and 1962.
Authorities in Warsaw, a conurbation of 2m people, urged residents of riverside districts to stay alert.
'The danger will grow. The flood-wave is longer than expected and could keep passing through the capital until Sunday evening. It's looking bad,' regional governor Jacek Kozlowski told reporters.
On the River Oder, in western Poland, the situation was not as serious as along the Vistula, Mr Tusk said.
He had earlier stated that he would not declare a state of emergency - a state of emergency would push back the presidential elections scheduled for 20 June.
By law, presidential elections must be held 90 days after the end of a state of emergency.