oneureun barami eobseoseo deol chuunga bwayo.

Yes:

• 오늘은 = today

  • topic marker -은
    → as for today / today

• 바람이 = wind

  • subject marker -이
    → the wind

• 없어서 = there is not / there isn't

  • because
    → because there is no wind

• 덜 = less

• 추운가 봐요 = it seems cold / I guess it’s cold
  In this sentence, with 덜, it becomes it seems less cold / I guess it’s less cold

So the structure is basically:

As for today, because there’s no wind, it seems less cold.

-은/는 marks the topic, not the subject.

So 오늘은 means something like:

• as for today
• today, ...

This is very natural when you are setting the scene or comparing today with other days.

It can also carry a slight contrast, like:

• Today is different from other days.
• Today, at least, it seems less cold.

If you used 오늘이, then today would sound like the grammatical subject, which is not the point here.

In 바람이 없어서, the noun 바람 is the subject of 없다.

So:

• 바람이 없다 = there is no wind

That is the most neutral and natural form.

If you said 바람은 없어서, it would sound more contrastive, something like:

• as for wind, there isn’t any...

That can work in some contexts, but it is not the default choice here.
So 바람이 is the normal option.

없어서 comes from 없다 + -아서/어서.

• 없다 = to not exist / to not be present / to not have
• -아서/어서 = a connector meaning because, so, or sometimes just linking actions/states

So:

• 바람이 없어서 = because there is no wind

Here it gives the reason for the next part of the sentence.

덜 means less or not as much.

So:

• 덜 춥다 = to be less cold
• 덜 맵다 = to be less spicy
• 덜 바쁘다 = to be less busy

It is often used as the opposite of 더:

• 더 춥다 = more cold / colder
• 덜 춥다 = less cold

In this sentence, 덜 추운가 봐요 means it seems less cold.

추워요 is a more direct statement:

• It’s cold
• or with 덜: It’s less cold

But 추운가 봐요 adds the meaning of guessing or inferring from what the speaker notices.

So -ㄴ/은가 봐요 means something like:

• it seems...
• I guess...
• looks like...

That makes the sentence softer and less absolute.

So the nuance is:

• 덜 추워요 = It’s less cold.
  (direct statement)

• 덜 추운가 봐요 = It seems less cold. / I guess it’s less cold.
  (observation or inference)

This is because 춥다 is a ㅂ-irregular adjective.

The basic dictionary form is:

• 춥다 = to be cold

But when certain endings are added, the ㅂ changes:

• 춥다 → 추워요
• 춥다 → 추운
• 춥다 → 추우면

So in 추운가 봐요, the 추운 part comes from that irregular change.

This is why it is 추운가 봐요, not 춥은가 봐요.

No. Here, 가 is not the subject particle.

It is part of the grammar pattern:

• -ㄴ/은가 보다
• polite form: -ㄴ/은가 봐요

This pattern means:

• it seems that...
• I guess...
• apparently...

So 추운가 봐요 is one grammatical chunk meaning it seems cold or I guess it’s cold.

Korean very often puts the background information or reason first, and then gives the main conclusion after it.

So this order is natural:

• 바람이 없어서 = because there is no wind
• 덜 추운가 봐요 = it seems less cold

This is a very common Korean pattern:

• 비가 와서 못 가요. = I can’t go because it’s raining.
• 시간이 없어서 못 했어요. = I couldn’t do it because I didn’t have time.

So the sentence order is completely normal.

Korean usually does not use a dummy subject like English it in weather expressions.

In English, you say:

• It is cold
• It seems less cold

But in Korean, you can simply say:

• 추워요 = It’s cold
• 덜 추운가 봐요 = It seems less cold

The subject is understood from context, so there is no need to say a separate word for it.

Yes. A few common alternatives are:

• 오늘은 바람이 없어서 덜 추워요.
  = Today, because there’s no wind, it’s less cold.
  More direct and certain.

• 오늘은 바람이 없으니까 덜 추워요.
  = Today, since there’s no wind, it’s less cold.
  Similar, but -으니까 can feel a bit more explanatory.

• 오늘은 바람이 없네. 덜 춥다.
  = There’s no wind today. It’s less cold.
  More conversational and casual.

The original sentence sounds natural when the speaker is noticing the situation and making a mild conclusion from it.