A Lunar Halo is a Hazy Circle Around the Moon.
Lunar (Moon) halos are the results of moonlight passing through ice crystals in cirrus or cirrostratus clouds that cover the sky. Folklore says that moon rings warn of appoaching storms. The number of stars within the halo predicts the number of days before the storm arrives. While, cirrus or cirrostratus clouds often appear a few days before a large storm front, one cannot rely on the clouds to predict storms because they can appear with no weather change.
22° Moon Halo
The Moon’s halo has a diameter of 22°, which is the angle that ice crystals refract the moonlight.
You can use your fist to measure the radius of the halo. Hold your fist at arms length. Point your fist at the Moon. The width of your fist is about 10°, which is a little less than the radius of the Moon’s halo.
You can use your outstretched hand to measure 20°, which is almost equal to the diameter of the Moon’s Halo.
44° Second Halo
Sometimes, a second halo can be seen. This second ring has a 44° diameter.
Lunar halos are usually colorless. But sometimes red is seen inside the halo and blue on the outside.