Prime Minister Giuseppe Conte described the flooding as "a blow to the heart of our country."
He said a cabinet meeting called for Thursday afternoon will declare a state of emergency and approve the first measures aimed at helping the city's recovery.
Conte spent Wednesday night in Venice, where world-famous monuments, homes and businesses were hit hard by the exceptional flooding. The water reached 1.87 meters above sea level Tuesday, the second-highest level ever recorded in the city.
Venice's mayor said the damage is estimated at "hundreds of millions of euros."