How rare is a sun halo?
Halos around the Sun and Moon are certainly not rare. They are caused by high cirrus clouds refracting light. Cirrus clouds are so high in the sky (typically higher than 20,000 feet), they are made up of millions upon millions of tiny ice crystals which readily refract the light from the Sun or Moon. Is halo around sun common? They are the collective glints of millions of crystals that happen to have the right orientation and angular position to direct their refracted light into your eye.