Abróchate la chaqueta antes de salir, que hace frío.

Because this is an affirmative tú command with a reflexive pronoun.

• Base verb: abrocharse = to fasten up / do up / button up oneself
• Tú command of abrochar: abrocha
• Add the reflexive pronoun te to the end: abrocha + te = abróchate

In affirmative commands, pronouns are normally attached to the end:

• siéntate
• levántate
• ponte
• abróchate

You do not say te abrocha here.

The written accent in abróchate is added to keep the normal stress in the right place after adding -te.

In Spanish, when talking about clothing, body parts, and personal items, it is very common to use the definite article (el, la, los, las) instead of a possessive like mi, tu, su, especially when it is already obvious whose item it is.

So:

• Abróchate la chaqueta = Fasten your jacket
• Literally, it looks like Fasten the jacket to yourself, but in natural English we say your jacket

This is very common:

• Lávate las manos = Wash your hands
• Ponte el abrigo = Put on your coat
• Quítate los zapatos = Take off your shoes

Abrochar means to fasten, to button, to do up, or sometimes to zip up, depending on the item.

So abróchate la chaqueta means something like:

• button up your jacket
• zip up your jacket
• fasten your jacket

It is more specific than just put on your jacket.

Compare:

• ponte la chaqueta = put on your jacket
• abróchate la chaqueta = fasten/button/zip up your jacket

The accent mark is there because when te is attached to the command, the word becomes longer, and Spanish adds a written accent to preserve the original stress.

Without the pronoun:

• abrocha → stress naturally falls on bro

With the pronoun added:

• abrochate would naturally be stressed differently if left without an accent

So Spanish writes:

• abróchate

This is very common with attached pronouns in commands:

• ponte
• siéntate
• mírame
• dímelo

Because in Spanish, antes is followed by de before an infinitive.

So the structure is:

• antes de + infinitive

Examples:

• antes de salir = before leaving / before you go out
• antes de comer = before eating
• antes de dormir = before sleeping

So antes salir is not correct.

Here que means something like because.

So:

• Abróchate la chaqueta antes de salir, que hace frío.

means:

• Fasten your jacket before going out, because it’s cold.

This use of que is very common in everyday Spanish, especially in speech. It often gives a reason in a natural, conversational way.

Compare:

• Ven, que te necesito. = Come here, because I need you.
• Cierra la ventana, que entra frío. = Close the window, because cold air is coming in.

In more formal or explicit wording, you could also say:

• ... porque hace frío.

Yes, but the difference is mostly about style and tone, not basic meaning.

• que hace frío sounds very natural and conversational
• porque hace frío is also correct, and it sounds a bit more explicit

In this sentence, que works very well because the speaker is giving a quick reason for the command.

So both are possible:

• Abróchate la chaqueta..., que hace frío.
• Abróchate la chaqueta..., porque hace frío.

The first one sounds especially common in everyday spoken Spanish.

Because Spanish often uses hacer in weather expressions.

• hace frío = it’s cold
• hace calor = it’s hot
• hace viento = it’s windy
• hace sol = it’s sunny

English uses it is..., but Spanish does not usually say es frío for weather in this context.

So:

• Hace frío = The weather is cold / It’s cold

Not in this structure.

After antes de, Spanish normally uses the infinitive when the subject is understood to be the same or when speaking generally:

• antes de salir = before going out / before you go out

You would use a finite verb only in a different structure, for example:

• antes de que salgas = before you go out

So both are correct in different patterns:

• antes de salir
• antes de que salgas

The version in your sentence is the simpler and more direct one.

Yes, it is natural and correct in Spain.

It sounds like something someone might say to a child, family member, or friend before going outside.

Depending on the situation, people might also say:

• Abrígate = Wrap up / Keep warm
• Ponte la chaqueta = Put on your jacket
• Súbete la cremallera = Zip it up

But Abróchate la chaqueta is perfectly natural if the idea is specifically to fasten it.

The comma separates the main instruction from the added reason.

• Abróchate la chaqueta antes de salir = main command
• que hace frío = explanation/reason

This pause is very normal in writing when que introduces a causal comment like this.

So the comma helps show the rhythm and structure of the sentence:

• command first
• reason second

The form abróchate shows that the speaker is talking to one person using tú.

So this is:

• informal
• singular
• used with someone you would address as tú

If the speaker were talking to:

• usted: Abróchese la chaqueta
• vosotros: Abrochaos la chaqueta
• ustedes: Abróchense la chaqueta

So the original sentence is clearly aimed at one person informally.