Cierra la ventana, que hace frío.

Cierra is the tú imperative of cerrar (to close), so it means close! when speaking to one person informally.

• Cerrar → cierra
• Example: Cierra la puerta. = Close the door.

A useful thing to notice: cierra also looks like the él/ella/usted present tense form (he/she closes, you close formal), but in this sentence the context makes it clear that it is a command.

Spanish usually uses the definite article (el, la, los, las) where English might sometimes leave it out.

So la ventana means the window. In this sentence, it refers to a specific window that both speaker and listener understand.

• Cierra la ventana = Close the window

Saying just Cierra ventana would sound unnatural in standard Spanish.

Because Spanish often omits subject pronouns when they are clear from the verb form.

In cierra, the command form already tells you the speaker is addressing you informally, so tú is not needed.

• Cierra la ventana = normal
• Tú cierra la ventana = possible, but more emphatic or contrastive

Spanish does this all the time:

• Hablo español. = I speak Spanish.
• Ven aquí. = Come here.

Here, que introduces an explanation: because / it’s just that.

So:

• Cierra la ventana, que hace frío. = Close the window, because it’s cold.

This use of que is very common in everyday Spanish, especially after commands or requests.

It is slightly different in feel from porque:

• Cierra la ventana, que hace frío. = very natural, conversational
• Cierra la ventana porque hace frío. = also correct, a bit more straightforwardly because

Both are fine, but the version with que is extremely common in speech.

Hace frío means it’s cold.

Literally, it may seem odd because hacer usually means to do or to make, but Spanish uses hacer in several weather expressions:

• Hace frío = It’s cold
• Hace calor = It’s hot
• Hace sol = It’s sunny
• Hace viento = It’s windy

So this is just a standard weather pattern you need to learn as a set phrase.

It is stem-changing.

Cerrar changes from e to ie in many forms:

• cierro
• cierras
• cierra
• cierran

That is why the command is cierra, not cerra.

For the informal singular imperative (tú), the form is normally based on the él/ella/usted present tense form:

• él cierra
• tú imperative: cierra

The comma helps show that que hace frío is an explanatory comment added after the command.

• Cierra la ventana, que hace frío.

The pause is similar to English:

• Close the window, it’s cold.
• Close the window, because it’s cold.

In writing, the comma is standard here. It makes the structure clearer and reflects the natural pause in speech.

Yes. If you are speaking formally to one person, you would use the usted command:

• Cierre la ventana, que hace frío.

If you are speaking to more than one person in Spain, you might use vosotros:

• Cerrad la ventana, que hace frío.

And for a formal plural:

• Cierren la ventana, que hace frío.

So the original sentence is specifically informal singular.

No, not naturally in this exact way.

The full statement is:

• Hace frío. = It’s cold.

In Cierra la ventana, que hace frío, the que links the explanation to the command. Without the main clause before it, que hace frío would feel incomplete in normal usage.

So:

• Hace frío. ✅
• Que hace frío. ❌ as a normal standalone sentence

In conversation, people sometimes use sentence fragments, but for learners it is best to think of que here as something that needs the previous clause.

Usually no, not for the weather.

• Hace frío = It’s cold (the weather / the environment is cold)

Está frío usually describes a thing being cold:

• La sopa está fría. = The soup is cold.
• El café está frío. = The coffee is cold.

So for weather or temperature in general around you, hace frío is the normal expression.

It is understood everywhere in the Spanish-speaking world, and the structure is broadly common.

The sentence sounds completely natural in Spain:

• Cierra la ventana, que hace frío.

In other regions, people may also say:

• Cierra la ventana porque hace frío.

So the original sentence is not uniquely Spanish, but the explanatory que is particularly common and very natural in everyday speech, including in Spain.