会 + 下雨 / 下雨 + 了
下雨 (xiàyǔ) means "to rain" and is the standard way to describe rainfall in Chinese. It is a verb-object compound that can be modified by adverbs of possibility or degree.
天气预报说明天要下雨,你带把伞吧。
tiānqì yùbào shuō míngtiān yào xià yǔ, nǐ dài bǎ sǎn ba.
The weather forecast says it will rain tomorrow; you should bring an umbrella.
刚才还是晴天,怎么突然下雨了?
gāngcái háishì qíngtiān, zěnme tūrán xià yǔ le?
It was sunny just a moment ago — how did it suddenly start raining?
连续下雨好几天了,衣服都没法晾干。
liánxù xià yǔ hǎo jǐ tiān le, yīfu dōu méi fǎ liàng gān.
It's been raining for several days in a row; the clothes can't dry at all.