Frost Feathers

After the rains of the early winter there's a little dampness in between our windows which is normally invisible and without effect. However, when the temperature drops it shows up as frost feathers at the bottom of the pane, and since the temperature outside is currently -13°C we wake up to this rather beautiful sight.
The area in the picture is about 10 cm high.  In the background the sun has risen (10 o'clock...ish) and is shining through a few trees.