What causes a ring around the moon?

What causes a ring around the moon?

Last night, I saw a ring around the moon.   A ring around the moon is also called a lunar halo.   What causes this  beautiful  sight?  It is not magic, or fairies dancing in a circle.  Moon halos are caused by  ice crystals in thin cirrus or cirrostratus clouds, high in the atmosphere.

According to the Farmers’ Almanac, weather lore says a lunar halo is the precursor of  unsettled weather, especially during the winter months.  This is often true, as cirrus and cirrostratus clouds usually  precede rain and storm systems.

According to EarthSky, the halo effect is a result of  refraction (splitting of light) and reflection from thousands of tiny  ice crystals.  As light passes through these hexagon-shaped ice crystals, it is bent at a 22 degree angle, creating a halo 22 degrees in radius (or 44 degrees in diameter).  The crystals have to be oriented and positioned with respect to your eye, in order for the halo to appear.

A prism effect of light passing through these six-sided ice crystals separates the light into its various colors, resulting in a halo tinged with very pale rainbow colors with red on the inside and blue on the outside. A  lunar halo is similar to a rainbow produced by sunlight and rain falling between your eyes and the sun.

As the poet said, “lovely snowflakes, they fall nowhere else,”  so too, the sight of the ring around the moon is  unique to your eyes, here and now.


Like this? Why not subscribe? Type your email address in the box and click the “create subscription” button. My list is completely spam free, and you can opt out at any time.

If you have Gmail, don’t miss out. Check your “promotions” box. Move one of my posts from the “promotions” box to “primary” and you’ll never miss a post. Thanks for reading!

Filed under: seasons, weather

Tags: lunar halo


Leave a comment
  • Thanks! Once again you lead me to wonder, in the best sense. I had just been assuming that lunar halos were effects of the lenses through which I (literally) usually see them. Thanks for the education.

  • In reply to Margaret H. Laing:

    Thank you for reading! So happy to share these things with you...

  • I was glad to read this. I thought those halos were just my old eyes not seeing things correctly!


  • In reply to Kathy Mathews:

    Thanks for reading, Kathy. Glad you enjoyed!

  • Thank God I always read you! I thought it was the Man in the Moon's shaving cream. Great post.

  • In reply to Aquinas wired:

    Ha, ha, ha, thanks, AW! I always thought it was the fairies dancing....

Leave a comment