We're used to unpredictable, fleeting weather changes in Chicago but this year, marked by the bizarrely mild winter, is throwing even the most composed among us for a loop. On Friday, the WGN weather center received several photos of a circmhorizontal arc in the sky, which can only occur when "the sun is high in the sky at 58º or higher above the horizon which at Chicago's latitude can only occur from about mid April to late August." It's a striking phenomenon, if a little alien in its spontaneous and shimmering glow. With so many weather records being set or broken lately, a little beauty is a welcome element.