If you plan to spend time in Venice during the fall and winter months, you may want to pack rubber boots. In Venice, flooding is a fact of life. Venetians call it “acqua alta” meaning “high water” -- and it refers to the occurrence of the higher than normal water levels of the Venetian lagoon infiltrating the city of Venice, causing water to overflow the edges of the canals and flood pedestrian walkways.
It happens when an unusually high tide pushes water from the Adriatic Sea into the Lagoon helped by southern winds and low atmosphere pressure. The flooding isn’t dangerous and it’s not considered a big deal; the water subsides within a few hours. In the past century it has become more frequent though and now it can happen any time of year.
During acqua alta you might have to step around a pond or two, but you can also buy boots in Venice from street vendors. The city provides elevated wooden walkways in areas that are prone to flooding; and you can see a map of these pedestrian routes at most ACTV vaporetto (Venice bus and water taxi) stops.
Acqua alta has never interfered with train travel in Venice. When the water level is predicted to rise above 110cm sea level, sirens are sounded. Venice's Tidal Center claims that its three-hour forecasts are 95% reliable, with an accuracy of plus or minus 10 centimeters. You can check for flood forecasts on the City of Venice's municipal website http://www.comune.venezia.it/maree/.
Photo credit: Rene Cunningham