Scientifically defined, a halo around the moon is simply "caused by the refraction of moonlight (which of course is reflected sunlight) from ice crystals in the upper atmosphere,"* but it means so much more...
Because, you see, God has promised that the rainbow "shall be for a token of a covanent between Me and the earth." (Genesis 9:13) Every rainbow represents a promise....
It would seem that the promises are only for when life is going well, since the rainbow is usually seen during the day. But in reality, like the rainbow, God's words are more stunning in the darkness, when life is not going well...
...That's the beauty of a promise.