22 May 2021

There were clouds on the eastern horizon when the sun rose in a spectacular sun pillar on Thursday morning 20 May.

According to Wikipedia (paraphrased):

The effect is created by the reflection of light from tiny ice crystals suspended in the air or in cirrus clouds.

The crystals are usually flat hexagonal plates that are oriented horizontally as they fall through the air. Each flake acts like a tiny mirror that reflects light sources positioned below it.

The presence of flakes at a spread of altitudes causes the reflection to be elongated vertically into a column. The larger and more numerous the crystals, the more pronounced this effect becomes. 

— Wikipedia article on light pillars

Though it was 57 degrees F at sunrise that morning, the sky was cold.

Sun pillars have a lot in common with sun dogs. They are both in the family of halos.