Det ser ud til, at skyerne bliver mørkere, og min nabo siger, at hun kan høre torden langt væk.

Det ser ud til is a very common Danish way to say it looks like or it seems that.

• det = it
• ser ud = looks
• til = part of the fixed expression

So:

• Det ser ud til, at skyerne bliver mørkere = It looks like the clouds are getting darker

The det here is a dummy subject, just like English it in it seems or it looks like. It does not refer to a specific thing.

You can think of ser ud til as one unit meaning seems/appears.

Both at words introduce a subordinate clause, and here they both mean that.

1. Det ser ud til, at skyerne bliver mørkere

   • that the clouds are getting darker

2. min nabo siger, at hun kan høre torden langt væk

   • my neighbor says that she can hear thunder far away

In everyday Danish, at is often optional after verbs like sige in some contexts, especially in speech, but it is very normal and clear to include it.

So this sentence uses at in a standard, natural way.

Skyerne means the clouds, while skyer means just clouds.

• en sky = a cloud
• skyer = clouds
• skyerne = the clouds

Danish often adds the definite article to the end of the noun:

• singular definite: skyen = the cloud
• plural definite: skyerne = the clouds

So skyerne bliver mørkere means the clouds are getting darker, not just clouds are getting darker.

Bliver mørkere means are becoming darker or are getting darker. It shows a change.

• bliver = becomes / gets
• mørkere = darker

So:

• skyerne bliver mørkere = the clouds are getting darker
• skyerne er mørkere = the clouds are darker

The version with bliver focuses on the process or change, which fits the weather situation well.

Yes. Mørkere is the comparative form of mørk.

• mørk = dark
• mørkere = darker
• mørkest = darkest

This is similar to English dark, darker, darkest.

A lot of Danish adjectives form the comparative with -ere:

• kold → koldere = cold → colder
• varm → varmere = warm → warmer
• mørk → mørkere = dark → darker

Because these are subordinate clauses, not main clauses.

In Danish main clauses, the finite verb is usually in second position:

• Min nabo siger ...
• Det ser ud til ...

But after at, Danish uses subordinate clause word order, where the subject normally comes before the verb:

• at skyerne bliver mørkere
• at hun kan høre torden langt væk

So the pattern is:

• at + subject + verb

This is different from normal main-clause V2 word order.

Kan høre means can hear and emphasizes ability or possibility.

• hun kan høre torden langt væk = she can hear thunder far away

If you said hun hører torden langt væk, it would mean she hears thunder far away. That is also possible, but kan høre often sounds more natural when you want to say that someone is able to perceive a sound.

So here kan adds the idea of being able to hear / managing to hear.

Here torden is being used in a general, uncountable sense, like thunder in English.

• høre torden = hear thunder

You are not talking about one thunder. You are talking about the sound or phenomenon in general.

This is very similar to English:

• I hear thunder not
• I hear a thunder

So no article is needed here.

Langt væk means far away.

• langt = far / a long way
• væk = away

Together they form a very common expression:

• langt væk = far away
• ikke langt væk = not far away

In the sentence:

• hun kan høre torden langt væk
• she can hear thunder far away

It tells you that the thunder is at a great distance.

Yes. Nabo can refer to a neighbor of any gender.

• min nabo = my neighbor

The noun itself does not tell you whether the person is male or female. That becomes clear later from the pronoun:

• hun = she
• han = he

So in this sentence, hun tells you that the neighbor is female.

It is a very common pattern in Danish. You can use it to talk about appearances, impressions, or guesses.

Examples:

• Det ser ud til, at det regner senere.

  • It looks like it will rain later.

• Det ser ud til, at han er træt.

  • It looks like he is tired.

• Det ser ud til at være svært.

  • It seems to be difficult.

Notice that you can sometimes have:

• Det ser ud til, at ...
• Det ser ud til at ...

Both are common, but the first version is especially natural when a full clause follows.

Yes. The commas are normal in Danish.

Danish usually places a comma before a subordinate clause introduced by at:

• Det ser ud til, at ...
• min nabo siger, at ...

There is also a comma before og here because it joins two larger parts of the sentence:

• Det ser ud til, at skyerne bliver mørkere
• og min nabo siger, at hun kan høre torden langt væk

So the punctuation is standard and helps make the structure clear.