Ice on Windows, Late Winter 2004
It has to get quite cold (-30 C) for a few days in order for this to happen. I've seen it 2 or 3 times now, in the 15+ years I've lived in this apartment.
Living room - sliding patio door. When it is this cold, I keep the curtains closed, which keeps down the heat loss through the window.
Note the hot water heating system right under the window!
The rest of the pictures are of smaller, higher windows.