What does " It was dark as night out, still storming." mean?

Question

I found the following sentences while reading the book "Let's Get Invisible" by R.L Stine. The book describes a birthday party on a rainy day. Near the end of the party the main character says:

I guess it was about five o’clock. It looked much later. It was dark as night out, still storming.

I'm wondering what does " It was dark as night out, still storming." mean. Does that mean the outside was dark similar to nighttime and it was still storming? If that is the case, I think the punctuation should indicate a pause after "night" and maybe use "still storming" in the next sentence.

Answer 1

The first part means it was very dark. It was the same darkness as nighttime. "Out" means "outside".

The second part tells you that the weather was a storm.

When there is a storm, the clouds make the sky dark.

Answer 2

These are all idiomatic ways of talking about the experience of being outdoors or the current conditions outdoors:

It was hot as hell out and very humid.

You should wear a heavier coat. It's freezing out.

It's really nice out. There's not a cloud in the sky.

No, you can't go out and play. It's dark out.

Bring your umbrella. It's still raining out.

But "out" is not a shortened form of "outdoors" and the word "out", when it refers to conditions outdoors, cannot appear at the head of a clause or phrase:

Out it was hot as hell and very humid.^{ungrammatical}

It was dark, out still storming. ^{ungrammatical}