Polar lights
Polar lights are sky luminous plays, which are to be seen in the higher latitudes nearby the poles, mostly during the longer nights ruling there. Polar lights are not weather phenomena, but lights which are released by electrically loaded particles emitted by the sun in the higher atmosphere layers.
Hence, polar lights are to be observed only with clear sky and mainly in the winter half of the year - warm clothes needed! There are also more chances to see them when the solar activity is particularly high (every 11 years, Milankoviç cycle). The polar lights are for many a reason to travel to the polar circles. The play that appears in the sky is indescribable.