During Thursday evening's winter weather in the St. Louis area and southern Illinois, a rare atmospheric optics phenomenon developed over much of the area. Light pillars are typically observed during extreme cold (near or below zero Fahrenheit) as tiny ice crystals hovering in the air near the surface reflect light from ground-level sources like streetlights. They appear very much like pillars seen during displays of aurora borealis, but their light source is terrestrial. What made this event unusual is that surface temperatures were in the upper teens to low 20s, and sleet was the precipitation type falling at the time. Sleet pellets are generally incapable of creating these type of optics themselves, so it is likely that the sleet was co-mingled with small ice crystals of another shape and size.
The pillars were visible over much of the St. Louis Metro East. This was the view at O'Fallon:
As I moved east on I-64 to stay with the falling precipitation, the pillars were visible over most towns in southern Illinois, most notably in Nashville:
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