3 sentences

1. 天气陡变，刚才还晴空万里，现在却下起雨来。

   tiān​qì dǒu biàn, gāng​cái hái qíng​kōng​wàn​lǐ, xiàn​zài què xià​qǐ yǔ lái.

   The weather changed suddenly; it was clear just a moment ago, but now it's raining.

   Source: Dong Chinese Dictionary

2. 刚才还是晴空万里，天气陡然变得阴冷起来。

   gāng​cái hái​shi qíng​kōng​wàn​lǐ, tiān​qì dǒu​rán biàn de yīn​lěng qi​lai.

   The sky was clear just a moment ago, but the weather suddenly turned cold and gloomy.

   Source: Dong Chinese Dictionary

3. 刚才还晴空万里，谁知道一下就下起了瓢泼大雨。

   gāng​cái hái qíng​kōng​wàn​lǐ, shéi zhī​dào yī​xià jiù xià​qǐ le piáo​pō​dà​yǔ.

   It was a clear, cloudless sky just a moment ago, then all of a sudden, it started pouring rain.

   Source: Dong Chinese Dictionary