Venice is located in North-East Italy so the climate is very different through out the year.
During the winter the temperature can drop below freezing, while in the summer the temperatures can soar to a dizzy 35 C / 96 F.
The hottest month is August and coldest month is January.

Because of the water that makes Venice so unique, the cooler temperatures feel colder and the warmer temperatures hotter.
During the fall and winter months Venice can suffer from flooding, that in November seems to occur almost on a daily basis. The flooding of Venice is directly related to tides in the Venetian lagoon.

So high water "aqua alta", normally only lasts a few hours a day.
Acqua Alta is a phenomenon that regularly occurs in the city of Venice, exspecialy during autumn and spring high tides. It involves the flooding of the most low lying areas of Venice, or, in more severe cases, up to 96% of the City streets.