天空大雨用英语可以翻译为 "heavy rain in the sky"。这个短语的来源可能来自于人们将雨形容为天空中落下的水，而 "heavy" 则是指雨水的大量。一些英文例句和中文翻译如下：
The sky was dark and cloudy, and soon enough, heavy rain started to fall. 天空变得阴暗而阴云密布，不久就开始下起大雨。
I quickly grabbed my umbrella and ran outside, but the heavy rain was already soaking me. 我迅速抓住雨伞冲出门外，但大雨已经把我淋湿了。
The weather forecast said that there would be heavy rain tonight, so I made sure to bring my raincoat. 天气预报说今晚会下大雨，所以我确保带上了雨衣。