Meaning: This means that the rain started unexpectedly and in a very intense way.
Choice of Words: Sudden is used to show that the rain started abruptly, without any warning. Heavily means that there is a lot of rain coming down.
Alternative Expressions
The rain started pouring all of a sudden.
Meaning: This means that rain started to fall unexpectedly and heavily. It's like saying, Rain started to fall out of nowhere and it was coming down really hard.
Choice of Words:Rain is the moisture condensed from the atmosphere that falls visibly in separate drops. Started means to start or commence. Pouring means to rain heavily. All of a sudden means unexpectedly or without warning. When you put them together, "The rain started pouring all of a sudden" means that rain started to fall unexpectedly and heavily.
Out of nowhere, it started raining cats and dogs.
Meaning: This means that rain started to fall unexpectedly and heavily. It's like saying, Rain started to fall out of nowhere and it was coming down really hard.
Choice of Words:Out of nowhere means unexpectedly or without warning. Raining means to fall as rain. Cats and dogs is an idiom that means heavily. When you put them together, "Out of nowhere, it started raining cats and dogs" means that rain started to fall unexpectedly and heavily.