What is the phenomenon that there is a fog circle next to the moon at night?

A halo around the moon is called "lunar halo". If you look closely, you will find that this halo is colored, the inner ring is red and the outer ring is purple. It is the aperture formed by the refraction of tiny ice crystals when the light of the moon passes through high and thin clouds (cirrus, cirrostratus or cirrocumulus). There will be a halo not only around the moon, but also around the sun. The formation principle is the same.

The appearance of dizziness usually means that the weather will change to some extent. Generally speaking, a solar halo means it may rain, while more lunar halos mean it will be windy. Sometimes there is a gap in the lunar halo, and the direction of the gap is the direction of the wind. Therefore, there is a folk proverb: "The sun is dizzy in the middle of the night and the moon is dizzy at noon."