Kan du sørge for at lukke vinduet, hvis det begynder at regne?

Yes, grammatically it is a question, but in everyday Danish Kan du ...? is very often used to make a polite request, just like English Can you ...?

So here it does not mainly ask about ability. It functions more like:

• Can you make sure to close the window ...?
• in natural use: Could you make sure to close the window ...?

This is a very common and polite way to ask someone to do something in Danish.

Sørge for at is a fixed expression meaning to make sure to, to see to it that, or to ensure that.

In this sentence:

• sørge for at lukke vinduet = make sure to close the window

You should learn sørge for at as a chunk, because the for is part of the expression here.

Examples:

• Kan du sørge for at ringe til ham? = Can you make sure to call him?
• Hun sørgede for at komme til tiden. = She made sure to arrive on time.

Because after sørge for at, Danish uses the infinitive form of the verb.

So:

• lukke = infinitive, to close
• lukker = present tense, close/closes

Here the structure is:

• Kan du sørge for at + infinitive

So:

• Kan du sørge for at lukke vinduet ...

not:

• Kan du sørge for at lukker vinduet ...

The same thing happens with begynder at regne:

• begynder = present tense
• at regne = infinitive

Because vinduet is the definite singular form: the window.

• et vindue = a window
• vinduet = the window

Danish often adds the definite article as an ending rather than using a separate word like English the.

So:

• lukke vinduet = close the window

This is very typical in Danish:

• en dør → døren = the door
• et hus → huset = the house

This det is an impersonal subject, similar to English it in weather expressions.

Just as English says:

• if it starts to rain

Danish says:

• hvis det begynder at regne

The det does not refer to a thing. It is just the grammatical subject needed for the weather expression.

You also see this in:

• Det regner. = It is raining.
• Det sner. = It is snowing.

Because begynde is normally followed by at + infinitive when another verb comes after it.

So:

• begynder at regne = starts to rain
• literally: begins to rain

More examples:

• Han begyndte at grine. = He started to laugh.
• Vi begynder at spise nu. = We are starting to eat now.

This is very similar to English begin/start to do something.

Hvis means if.

So:

• hvis det begynder at regne = if it starts raining

You might also hear når, which usually means when. The difference is roughly:

• hvis = if, condition, maybe it will happen and maybe not
• når = when, expected or assumed to happen

So:

• Hvis det begynder at regne ... = If it starts raining ...
• Når det begynder at regne ... = When it starts raining ...

In your sentence, hvis suggests a condition rather than something certain.

Because hvis det begynder at regne is a subordinate clause, and Danish word order in subordinate clauses is usually more like English.

So you get:

• hvis det begynder at regne

with the subject det before the verb begynder.

This is different from main clauses, where Danish often has verb-second word order.

Compare:

• Det begynder at regne. = main clause
• ..., hvis det begynder at regne. = subordinate clause

So the order here is completely normal.

Yes. If the subordinate clause comes first, the main clause follows normal Danish verb-second rules.

Original:

• Kan du sørge for at lukke vinduet, hvis det begynder at regne?

With the if-clause first:

• Hvis det begynder at regne, kan du så sørge for at lukke vinduet?

or simply:

• Hvis det begynder at regne, kan du sørge for at lukke vinduet?

The important thing is that after the fronted clause, the finite verb in the main clause comes early:

• ..., kan du ...

It is generally polite and normal, especially in everyday speech.

It sounds like a practical request, not rude. Danish is often a bit more direct than English, but Kan du ...? is still a common polite form.

Depending on tone and context, you could also hear:

• Vil du sørge for at lukke vinduet ...? = Would you make sure to close the window ...?
• Kan du lige lukke vinduet ...? = Can you just close the window ...?

Your sentence sounds natural and courteous.

No, not in standard Danish.

The idiomatic expression is:

• sørge for at ...

So you need the for here.

Correct:

• Kan du sørge for at lukke vinduet?

Not standard:

• Kan du sørge at lukke vinduet?

It is best to memorize sørge for at as one unit.

Yes, a very important one.

• lukke = close
• slukke = turn off / extinguish

So:

• lukke vinduet = close the window
• slukke lyset = turn off the light

English speakers sometimes confuse these because both can feel like “shut” in English. But for a window, you use lukke, not slukke.

A helpful breakdown is:

• Kan du = Can you
• sørge for at = make sure to
• lukke vinduet = close the window
• hvis = if
• det begynder at regne = it starts to rain

So the structure is basically:

Can you + make sure to + close the window + if it starts raining?

This is a very natural Danish pattern:

• polite request in the main clause
• condition in the hvis-clause