While lunar halos aren’t that unusual, they are not as common as halos appearing around the sun. Avid skywatchers may detect around 10 such events in a year.
Halos are created by light refracted through ice crystals 10 kilometres above the earth.
Ursa’s Juha Ojanperä said that the best time to observe the halo is close to the full moon. The lunar halo will be visible in the heavens for several weeks, as long as it’s not obscured by heavy cloud cover.