Question: In south Texas, I saw the largest ring around the Moon I've ever seen. Why so big and does it predict weather?
Answer: The ring around the Moon (and sometimes the Sun) is called a halo. The most common halos are caused by hexagonal ice prisms where the light enters and exits through one of the side faces and the halos have a diameter of 44 degrees. A quite rare form of halo is produced by cubic ice crystal or by hexagonal ice prisms where the light goes through the end faces of the prism and this halo has an diameter of 92 degrees. I am sure you saw this 92 degree halo in that clear Texan night-a rare event. In 60 years of observing the nigh sky, I have only seen this twice. As far as I know, it has no weather prognosticating indications.