Don’t read any of the other explanations, they just spout off the same thing they want you to think!
I did my own research, it turns out this is due to ice crystals. The inside of the dome set on top of the flat earth is covered by LCD displays. These displays get cold in wintertime and ice crystals form within the displays. This causes all sorts of visual glitches, like these halos around the moon. When it warms back up the ice crystals go away and the moon looks normal again.
Don’t let people fool you with bullshit stories about ice crystals in the so called atmosphere. It’s a totally made up story, with just enough truth in it to make it believable.