It's easy to see what appears to be daily freeze-thaw cycles of these sunlit icicles hanging from a window of my home in North Tonawanda, New York Brutally cold weather throughout the winter, combined with the southern exposure of the window and the warmer air coming from my house, ensured that the icicles would last for many weeks. The tight rings seems to show that melting was quite slow, though persistent, as air temperatures seldom exceeded the freezing mark during the entire month of February 2015. However, it should be noted that while the diurnal cycle certainly has an effect on icicle formation, other factors likely caused the ripples to form. Photo taken on February 23, 2015.