天気が急に変わった。

weather; the elements; fair weather; fine weather

indicates sentence subject (occasionally object); indicates possessive (esp. in literary expressions); but; however; still; and

urgent; sudden; abrupt; sharp; steep; precipitous; rapid; swift; fast; emergency; crisis; hurrying; haste; (in gagaku or noh) end of a song

at (place, time); in; on; during; to (direction, state); toward; into; for (purpose); because of (reason); for; with; by; from; as (i.e. in the role of); per; in; for; a (e.g. "once a month"); and; in addition to; if; although

to change; to be transformed; to be altered; to vary; to move to; to be different; to be uncommon; to be unusual