The exact meaning of this idiom!

[Johnny]

The idiom I'm going to talk about is:
It never rains but it pours.

The English explanation is similar as when things go wrong, they are very wrong.

It sounds that it's something bad or derogatory.

I checked some Chinese websites and found that some explanations(Chinese idioms too) are something as follows:
1: mishap never comes single
2: Someone who appears ordinary, but he would become extraordinary(exceptional or phenomenal) when he shows his true color. It means someone is very good, has a lot of potential.

My question is can I describe people or things good by using this Idiom? I mean It never rains but it pours.

[dani6nv]

This is a variation on the english idiom "When it rains, it pours."

Definition:
When it rains, it pours: When one thing goes wrong, many other things also go wrong.

Example:
Last week my dog ran away, and my computer crashed and my girlfriend broke up with me! When it rains, it pours!

here's how another website put it....
(it never) rains but it pours/when it rains it pours


- problems often appear together in large numbers or quickly one after the other

It is true that it never rains but it pours and our winter was spent dealing with problem after problem caused by the new accounting system.

" When it rains, it pours "

Adage Meaning - Misfortunes seldom come alone

Hope this helps!

[Tdol]

I've not herad it used in a positive way and the Cambridge dictionary of idioms only gives it in a negative sense:
Cambridge Dictionaries Online - Cambridge University Press

[dani6nv]

I'm an American and I've never heard it used in a postive way.
It's always been used to describe a series of bad or unfortunate events.

[Johnny]

You guys did me a great favor.

I did think that it should mean bad things, unluckiness. But I saw the horrible Chinese explanation on some sites. That's why I raised this question for proof.

Thank you, I got a variation from Dan and It has just been proved that it can only used in a negative way.