In Polish mythology, sky women were the warm-weather incarnations of the rusalki. Slavic women would go out in the first snowfall and build snow women to honor them, as snow is believed to be brought by the sky women. One belief has it that the thunder and lightning of springtime are brought on by Sky Women mating with the thunder gods; hence spring festivals included a celebration of the return of the rusalki from the waters with the placing of wreaths on the waters, and with circle dances and fire festivals.