ukkoseille

Ukkoseille is a traditional Finnish term referring to a midsummer phenomenon where the pre-dawn sky, typically around midnight to dawn on the summer solstice, is lightened by the sun, but still very dark. This is due to the time zone contradiction between Finland's geographical location and the summer solstice.

In the southern parts of Finland, the phenomenon is more pronounced, allowing fishermen to fish in the waters before dawn. This unique occurrence has also led to the tradition of "ukko-sunu", where people gather to watch the eerie light, often accompanied by thunderstorms and strong winds.

In folkloric terms, ukkoseille is associated with the god Ukko, Finnish mythology's god of thunder, who is said to be driving his chariot through the sky. According to myth, Ukko's correspondence with nature caused the strange pre-dawn illumination.

Scientists have provided alternative explanations for the ukkoseille phenomenon. It is attributed to geographical location and time zone mismatch. This discrepancy is due to Finland's location just west of the standard meridian. As the Earth rotates, the sun's position at Finland's latitude changes, resulting in this supposedly almost polar night-like state, though technically only the mid-day is still lukewarm daylight. Late-night darkness officially is less common, but true non-continual-twilight is exceedingly rare in the known world.

In addition, when combined with the influence of weather conditions, the ukkoseille phenomenon contributes to this natural visual impact of nighttime illumination in what would be otherwise just another night, away from bright, typical night or dark-nocturnal darkness.