Why does Venice flood in the midst of summer?

It just happened a few days ago ..

Acqua alta is a phenomenon we expect in autumn and early winter, when tides change TWICE a day (TWO PEAKS of high tide per day). It happens less often and less pronounced in summer when the tides change somewhat irregularly but just ONCE a day (ONE PEAK of high tide a day).

However, there have always been exceptions to this rule, and they seem to happen more often during the past decade. Acqua alta is brought on by heavy southerly winds called SCIROCCO pressing the water from the sea into the Lagoon, pronounced during FULL MOON and NEW MOON.

So you must also expect some floods during summer, but often, they will appear as a couple of large pozzanghere (puddles).

Is this month’s acqua alta different from earlier ones in summer?

This time, for a couple of hours during four days, all parts of Piazza San Marco were flooded. Usually, just lower parts will flood, as you can see in the images (July 2019), where there are still a few dry spots left where the people stand.

This time, in addition to the Piazza, other low-lying areas of the city were also hit by the flood, which happens rarely in summer.

Acqua alta in summer

Was Venice hit by the heat wave of last month?

Contrary to other parts of Italy, the Veneto was rather hit by floods than by extreme temperatures. So far this summer, temperatures haven’t been too high.

But then, you can notice that during the past ten years or so, summers become less „reliable“ here, and storms heavier. For example, I recall particularly cold summer weeks in 2014, when temperatures were around 14 degrees Celsius in the morning and barely reached 25 at noon.

As of now, we cannot predict how the Lagoon will fare in the future, whether there will be rather heat or flooding, or both.

Also, the number of tornados hitting the coastline seems on the rise: Tornadoes used to happen every 10-15 years until the 1990s, while by now, we witness several ones per year.

Understanding the nature of the Lagoon

This is the first part in the series “Understanding the Lagoon of Venice”. Next Monday, we’ll talk about how Venice fared during the climate change in the Medieval Age, and what we can learn for the future.