A rainstorm is a storm made of rain: a sudden, heavy fall of rain, often with wind, and often over quite quickly. People say it when the sky opens and the rain comes down hard — not for a light drizzle, and not for quiet rain that lasts all afternoon. Though actually, speakers stretch it a little. A long, serious spell of heavy rain can also be called a rainstorm, not only a short burst. It is an ordinary word, not fancy; you hear it in speech and in the weather news. It feels a bit stronger than “heavy rain”: there is weather in it, not only water falling.

暴風雨