The best months to visit Venice are April, May, June and early September. The
city generally enjoys mild winters and warm summers but extreme situations can
occur: hot and humid in summer and extreme cold days in winter are not uncommon.
Flooding (acqua alta) can occur at any time, particularly between November and
March: a system of sirens will alert the population of incoming water and newspapers
will print alerts and forecasts daily. "Walking the plank" takes a new meaning
in Venice, where boards are deployed to allow movement between the main points
of the city when the sea water rises. A good pair of boots is a must in these
situations.
Fog is another problem between September and January and public transport is
sometimes suspended when visibility is severely reduced. However, for the romantic
couple, walking in Venice on a foggy day is the thing to do; the views are surreal
and the ghostly passers-by suddenly appearing and disappearing before your eyes
will give you an eerie feeling.