also: はくや
noun
midnight sun; white night
Refers to the natural phenomenon at high latitudes where the sun remains visible at midnight. Used in both literal and figurative contexts.
北欧では夏に白夜が続く。
In Northern Europe, the midnight sun continues in summer.
白夜の下で一晩中歩き回った。
We walked around all night under the midnight sun.
極夜 is the polar night when the sun never rises, opposite of 白夜.
From 白 (white) + 夜 (night), literally 'white night'. The term is a calque from European languages describing the phenomenon of the midnight sun.