säieleen

Säieleen is a term used in Finnish to describe a phenomenon related to the moon's appearance. It literally translates to "rainbow moon" or "moonbow." This meteorological and optical phenomenon occurs when moonlight is refracted and reflected by water droplets in the air, similar to how a rainbow is formed by sunlight. Säieleen are typically seen during full moons when the moon is low in the sky, and there is sufficient moisture present, such as from rain, mist, or spray from waterfalls.

The appearance of a säieleen is often fainter than a solar rainbow due to the lower intensity of moonlight compared to sunlight. They are usually white or pale in color, though some observers have reported seeing faint colors. The phenomenon is relatively rare and requires specific conditions to be visible. Historically, säieleen were sometimes associated with folklore and omens in various cultures, though modern understanding attributes them solely to atmospheric optics. They are most commonly observed in tropical regions where frequent rainfall and clear skies coincide with full moons.