Ice crystals By Matt Young January 2, 2023 12:00 MST Ice crystals on a window during the recent cold snap, December 23, 2022, at around 7:40 a.m. The window is nearly 2 m tall and double-paned. It sits behind an insulated Roman shade known as a Warm Window, so it gets very cold near the bottom. The hills are a few millimeters across and melt very quickly once the shade is pulled up.