A Moonbow Forming Over Snow

 A Moonbow Forming Over Snow-Covered Peaks .. A Rare Nighttime Optical Phenomenon

What you’re seeing is a lunar halo created when moonlight passes through millions of tiny ice crystals suspended in the upper atmosphere.
Each crystal bends the light at a fixed angle — usually 22° — producing a faint arc that becomes visible only when the Moon is bright enough and the air is cold and clear.

low temperatures, hexagonal ice crystals, and a high-altitude Moon aligned just right above the mountains.