Acqua alta in Venice: tide forecasts, MOSE and what to do
Practical guide to acqua alta in Venice: how to read tide forecasts, why St Mark’s gets wet first, how MOSE works and what visitors should do.
Acqua alta is a temporary rise in the tide and does not mean that all of Venice is flooded. Different parts of the city sit at different elevations, so low areas can be wet while many streets remain normally usable. The most useful information is the forecast level and the time of the peak.
How to read the tide forecast
Venice tide levels are referenced to the Punta della Salute tide gauge. The official Tide Centre classifies 80–110 cm as sustained tide and 110–140 cm as very sustained tide, among other bands. A single number still does not describe conditions everywhere: local elevation matters.
Why St Mark’s Square gets wet first
Parts of the St Mark’s area are among the lowest points in the historic city, so water may appear there while many other districts remain dry. Photographs of the square should not be read as evidence that the whole city is underwater.
MOSE: avoid relying on one “magic” number
MOSE is the mobile-barrier system at the lagoon inlets. The barriers can temporarily separate the lagoon from the Adriatic when significant high tides are forecast. Operations depend on forecasts and operating criteria, so visitors should follow official tide information rather than assuming that one fixed number explains every activation.
Sirens and warnings
Venice uses an audible warning system with different signals linked to expected tide levels, including 110, 120, 130 and 140 cm and above. These are information tools, not a sign that visitors must leave the city.
What to do on the day
Check the expected maximum and its time, follow the Tide Centre updates and look for any vaporetto changes. If a low area is affected, changing route or waiting for the tide to fall is often enough; do not plan the whole day around old photos or outdated reports.
Marghera Venice Apartments tip
Before changing your plans, check two things: the forecast level and the peak time. Use the City of Venice Tide Centre on the day of your visit.
Official information
Times, access rules, reservations and transport arrangements can change. Check variable details with the official source before your visit.
Venice Tide Forecasting Centre – City of Venice ↗A convenient base for Venice
Visiting Venice for this event?
Stay in Marghera with free private parking and convenient day-and-night connections to Venice.