The rain is coming down, the lightning hits and there's thunder.

大雨倾盆，电闪雷鸣。

youdao

The rain is coming down in sheets.

大雨滂沱。

《新英汉大辞典》

The rain is coming down.

雨开始下了。

youdao

and the rain is coming down, the lightning hits and there's thunder.

大雨倾盆，电闪雷鸣。

I'm afraid of 课堂 - SpeakingMax英语口语达人

But basically, the rain is coming, it's hitting the mountains and it's just coming racing down into the valley, into the rivers, overflowing the rivers, and flooding the city.

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