。
It snows day after day.
Literal
Come day [also-も] come day [also-も] snow [subject-が] is-falling.
来る日も来る日も is a poetic/literary set phrase meaning 'day after day / day in and day out,' literally 'coming day, also coming day.' The repetition with も emphasizes monotonous repetition. Often used in narrative or reflective prose.