Forecasts have said that, at its peak, the 'aqua alta' ("high water") as it is known in Venice, would reach 160 cm later in the day propelled by strong and gusty winds that are pushing the water from the lagoon into the city.
City officials have removed the walkways that are normally placed over St Mark Square because, with such high tides, they would float into the water, creating safety concerns.
Public transport services have been suspended, authorities said on Twitter, and for the fourth consecutive day schools and education centres have remained closed.
Venice, a World Heritage Site, was flooded on Tuesday night by a tidal surge of 187 cm, the highest level since 1966, when a 194 cm tide was recorded.
High tides will persist throughout the week with some 85 to 120 cm expected.
The former Minister of the Interior and leader of the far-right Northern League Matteo Salvini has arrived in the city.
On Thursday former President and founder of Forza Italy, Silvio Berlusconi also visited the flooded city.
On the same day, the Italian Council of Ministers issued a state of emergency in Venice and approved a first-aid bundle of 20 million euros for those affected by rising tides.
Prime Minister Giuseppe Conte said that 5,000 euros will be offered to each affected resident and up to 20,000 euros to business owners.
St Mark's Basilica is of particular concern because it stands at one of the lowest points in the city and will suffer from floods again.
Following Tuesday's tidal surge its crypt was completely flooded, the marble sarcophagus was swamped and its mosaics were drenched in water.