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When there's a sunset glow, the next day is often sunny.
Literal
Sunset-glow [subject-が] exist-[conditional-と], next-day [topic-は] clear-[nominal-ことが] many.
A piece of folk weather wisdom — worldwide, a red sunset often predicts fair weather the next day. The structure ~ことが多い ('there are many times when X / X is often the case') is a useful general-tendency pattern. 翌日 ('the next day, the following day') is more formal than 明日 — used for reporting or narrative contexts.