oneureun chuwoseo mokdorireul haeyo.

은 is the topic marker. In 오늘은, it means something like as for today or today, at least.

So 오늘은 추워서 목도리를 해요 has a nuance like:

• As for today, it’s cold, so I wear a scarf
• Today, since it’s cold, I’m wearing a scarf

Using 은 can also suggest a slight contrast, even if it is very mild:

• Today is cold
• maybe other days are not

If you used 오늘이, it would sound more like today is the grammatical subject, which is less natural here.

-아서/어서 connects two parts of a sentence and often means because or so.

Here:

• 추워서 = because it is cold / since it is cold
• 목도리를 해요 = I wear a scarf

So the sentence structure is:

• 오늘은 추워서 = Because it’s cold today
• 목도리를 해요 = I wear a scarf

This grammar is commonly used when one situation naturally leads to another.

The dictionary form is 춥다, which means to be cold.

When adding -어서, it changes like this:

• 춥다
• stem: 춥-
• irregular change: 춥 → 추우
• then contract: 추우 + 어서 → 추워서

So 추워서 is the natural connected form of 춥다.

This happens because 춥다 is a ㅂ-irregular adjective.

A few similar examples:

• 덥다 → 더워서
• 어렵다 → 어려워서

In Korean, different kinds of things are worn with different verbs.

For example:

• 옷을 입다 = wear clothes
• 모자를 쓰다 = wear a hat
• 신발을 신다 = wear shoes
• 안경을 쓰다 = wear glasses
• 목도리를 하다 = wear a scarf

So for scarves, 하다 is very common.

Literally, 하다 usually means to do, but with some accessories and items you put on your body, it can mean to wear.

So:

• 목도리를 해요 = I wear a scarf / I’m wearing a scarf

Because 목도리 is the object of 하다 in this expression.

• 목도리 = scarf
• 목도리를 하다 = to wear a scarf

Here, 를 is the object marker.

So:

• 목도리 = scarf
• 목도리를 = scarf + object marker

Even though in English we say wear a scarf, in Korean this expression is built with 하다, so the scarf is treated as the object of that verb.

Korean often leaves out the subject when it is obvious from context.

So 오늘은 추워서 목도리를 해요 usually means:

• I wear a scarf because it’s cold today
• or I’m wearing a scarf because it’s cold today

But depending on context, it could also mean:

• we wear scarves
• she is wearing a scarf
• people wear scarves

In normal conversation, listeners usually understand the subject from the situation.

해요 is:

• present tense
• polite style
• often called informal polite

So it is a very common everyday form.

It can mean:

• I wear a scarf
• I am wearing a scarf

Korean present tense often covers both a general action and an action happening now, depending on context.

It can mean either one, depending on context.

Possible interpretations:

• Because it’s cold today, I wear a scarf
• Because it’s cold today, I’m wearing a scarf

In everyday Korean, the plain present form often does both jobs.

If the speaker wants to make the action feel more clearly ongoing right now, they might say something like:

• 목도리를 하고 있어요 = I’m wearing a scarf

But 목도리를 해요 is still very natural.

Yes. -아서/어서 can be translated in several natural ways in English:

• because
• since
• so

So 오늘은 추워서 목도리를 해요 could be understood as:

• Because it’s cold today, I wear a scarf
• Since it’s cold today, I’m wearing a scarf
• It’s cold today, so I’m wearing a scarf

The exact English wording depends on what sounds most natural in the situation.

Yes, you could.

• 추워서 and 추우니까 can both express a reason

But there is a slight difference in feel:

• 추워서 sounds more like a natural cause-and-result connection
• 추우니까 can sound a bit more like the speaker’s reasoning, judgment, or justification

So:

• 오늘은 추워서 목도리를 해요 = It’s cold today, so I wear a scarf
• 오늘은 추우니까 목도리를 해요 = Since it’s cold today, I wear a scarf

Both are correct, but 추워서 feels very smooth and natural here.

Yes. 목도리 is a noun meaning scarf.

Examples:

• 목도리예요 = It is a scarf
• 목도리를 해요 = I wear a scarf
• 목도리가 예뻐요 = The scarf is pretty

So in your sentence:

• 목도리 = the scarf itself
• 를 = object marker
• 해요 = wear it / put it on

Together, 목도리를 해요 means wear a scarf.