Few times a year, mainly in autumn and winter, the phenomenon of "Acqua Alta"(high tide) in Venice can occur: particular weather and astronomical conditions cause the water of the famous lagoon to raise its level, going to submerge part of the city, especially in the lower points.
In recent years it has happened very rarely that the tide reached an increase of 110 cm. In that case the water submerges just over 10% of the city. Even more rarely happens that the tide exceeds 130 cm, in that case to be submerged by water is about 60% of the historic center, with a level of water ranging from a few centimeters, up to 60 of St. Mark's Square, the lowest area of the city.

The phenomenon is manageable: the transports allow to move quietly and the main places of the city can be reached through raised pedestrian routes. In any case, to prevent high tide from ruining your stay in Venice, it may be useful to find out how to understand when high tide comes and how long it lasts, how to equip yourself for high tide, the areas affected by the phenomenon but, above all, what to do in Venice when there is high tide. Let's go and find out.

When does high tide in Venice come and how long does it last?

When does the high tide come to Venice? What causes it? There is no single answer: this phenomenon is caused by various climatic, meteorological but also astronomical factors, which occur mainly in autumn and winter. One of the factors is the winds that blow over the lagoon, such as the sirocco winds, which move masses of water from the Adriatic sea to the Venice basin, while another meteorological factor may be a low-pressure area in the north of the Adriatic and a high-pressure area in the southern Adriatic, which favour a shift of water and, therefore, an increase in the level. The water level is also affected by the astronomical high tide factor, which, although less pronounced than in the ocean, can combine with meteorological factors and have a strong impact on the water level.

The Il centro previsioni e segnalazioni maree del comune di Venezia (tide forecasting and reporting centre of the municipality of Venice) is able, by analysing these factors, to predict and report tides and their intensity. The reports are made through warnings and sirens and are published on the site of the center: https://www.comune.venezia.it/content/centro-previsioni-e-segnalazioni-maree
If you are wondering how long high tide lasts in Venice, the answer is very simple: it follows the normal cycle of tides, lasting 12 hours, divided between an ascending and a descending phase. The actual hours of flooding coincide with the 3-4 central hours of this cycle.

High water in Venice: which are the areas affected

If you think that all of Venice is submerged every time there is high tide you are wrong: the phenomenon touches the various areas of the city in different sizes depending on the height so knowing which are the areas affected by high water in Venice is a 'piece of information that could save the day.

There are areas of the city that flood more easily, such as the area of San Marco and its surroundings, the lowest in the city, and the Dorsoduro district. Other areas that are easily submerged are those of Rialto and Punta della Salute. However, in most cases the tide reaches a height that covers about 3-4% of the surface of the city and are rare times when a larger portion is flooded.

To be clear, here is a table with the percentages of "submerged city" according to the height of the tide: +100 cm: 3.56%; +110 cm: 11.74%; +120 cm: 35.18%; +130 cm: 68.75%; after 140 cm the city is flooded for more than 90%.

How to equip yourself to deal with high tide in Venice

We have seen that high tide is a more than manageable phenomenon but to minimize the risk of inconvenience is right to know how to equip  to deal with high water in Venice.
Assodato that in most cases the tide touches only a small part of the city, to be able to visit just get rubber boots high up to the knee. You could also opt for "pocket boots", similar to bags, but with the sole, which are foldable and comfortable to carry in your bag. You can buy both the latter and normal boots once you arrive in Venice, in any of the shops in the area of the station or Piazzale Roma. Be careful, at high tide the price of the boots could rise together with the water level. 
To know when you should wear or take your boots with you, you can refer to the signalations of the tide center.

What to do in Venice with high tide

Considering that high tide often affects small portions of the city, if you are wondering what to do in Venice with high tide, in most cases the answer is: all you would do without high tide. The city of Venice also has a system of elevated walkways that makes it possible to reach most of the historic center even in case of high tide. Even the transport system is able to ensure an easy trasportation.

The advice, therefore, is not to be conditioned by this phenomenon of high tide with which the Venetians have lived for years without particular problems and to take advantage to visit those places that the high tide can make more attractive, such as the library Acqua Alta.

Moreover, even in case of exceptional tide, the high tide lasts about 3-4 hours. You could even take advantage of it, wear your boots and enjoy a unique experience: walking through the streets and buildings of a city submerged by water, an experience that you will carry in your heart forever and that only one place in the world can offer you.  That place is Venice.