。
It sounds like it'll rain tonight.
Literal
Night [topic-は] rain [to-に] become-[hearsay/evidence-らしい].
~らしい is the evidential/hearsay marker — 'seems like X, I hear that X.' Subtly different from ~そうだ (hearsay) and ~ようだ (appearance-based inference): らしい leans toward reported information or typical characteristic. 雨になる ('turn to rain, become rainy') is the standard way to say 'start raining' as a weather change.