I was in Venice once in early June and it was spectacular. So Sunny and brilliant..hot in the sun, cool in the shade and it stayed light until nearly 22:00/10PM each night. You could see the mountains from the north side of Cannaregio.
I was also there in mid-October and it was wet and cloudy but theres something wonderful about that as well.
I always wanted to go when it empty and haunted and there was a chance of snow. This is that trip.