A circle or ring around the moon is usually a lunar halo , caused by moonlight passing through millions of tiny ice crystals high in Earth’s atmosphere, not by anything happening to the moon itself.

What that circle really is

When you see a big ring around the moon, you’re almost always looking at:

  • A “22-degree halo,” an optical effect where light is bent about 22 degrees as it goes through hexagon-shaped ice crystals.
  • An atmospheric phenomenon similar to a faint rainbow, but created by ice, not raindrops.

This makes the sky itself act like a giant lens, drawing a pale circle around the moon.

How the halo forms

High, thin clouds called cirrus or cirrostratus drift 20,000 feet or more above the ground and are made of ice crystals instead of liquid droplets.

  • These crystals work like tiny prisms and mirrors, bending and sometimes reflecting the light.
  • Because most crystals are hexagonal, the bending angle is very consistent, giving the ring a nearly fixed apparent radius of about 22 degrees (roughly the width of your outstretched hand at arm’s length).

That’s why halos around both the sun and the moon tend to be the same apparent size in the sky.

Why it sometimes looks colorful

Even if the ring looks mostly white, it is created by the same basic prism effect that produces rainbows.

  • Longer-wavelength red light is bent slightly less, so it tends to show on the inner edge of the halo.
  • Shorter-wavelength blue light is bent a bit more, appearing toward the outer edge.

Moonlight is much dimmer than sunlight, so the colors are usually too faint for the eye and the halo appears milky or grayish.

Does it mean a storm is coming?

For a long time, many cultures treated a ring around the moon as a weather sign, often saying it meant bad weather was on the way.

There is a grain of truth:

  • The ice-crystal clouds that create halos frequently form ahead of approaching warm fronts and low-pressure systems (storms).
  • So a halo can sometimes appear a day or two before rain or snow, especially in colder seasons.

However, not every moon halo leads to storms, so it is a suggestive hint, not a reliable forecast tool.

Why this topic is trending

Photos of “crazy circles around the moon” regularly show up in forum discussions and social feeds, especially:

  • During full or nearly full moons, when the halo is brightest.
  • In winter or in places with frequent high, icy clouds, making halos more common.

Online threads often mix scientific explanations (ice crystals and refraction) with folklore (“count the stars inside the ring to know when it’ll rain”), reflecting how this one simple sky effect sits between everyday weather lore and atmospheric physics.

Information gathered from public forums or data available on the internet and portrayed here.