Nightly, nocturnal, night all mean of, relating to, or associated with the night.
Nightly, opposed to daily, may mean no more than this. But nightly is the one of these terms that usually carries a strong implication of recurrence and is especially appropriate to convey the idea of happening night after night.
Nocturnal, opposed to diurnal, is often interchangeable with nightly, especially in its more general sense, but distinctively it may mean active at night.
Night in much of its use is interchangeable with nocturnal and may be preferred to the latter when a less formal term is required. Distinctively, the term is used to describe persons who work at night and things that occur or are intended for use at night.