Kad zahladi, navečer se volim prekriti toplim poplunom.

Kad means when. It is a very common shorter form of kada.

In most everyday Croatian, kad and kada mean the same thing. Kada can sound a bit more formal or a bit more emphatic, while kad is extremely natural in normal speech.

Here zahladi means it gets cold, it turns cold, or the weather becomes colder.

The prefix za- often gives the idea of starting a new state or a change beginning, so zahladi has the sense of it starts being cold.

After kad, Croatian often uses the present tense to talk about something that happens whenever a situation occurs or when it happens in the future.

So Kad zahladi is naturally understood as When it gets cold or Whenever it gets cold.

There is also no separate word for English it because Croatian weather expressions are often impersonal. English says it gets cold, but Croatian can simply say zahladi.

Navečer means in the evening.

It is very close in meaning to uvečer, and in many situations they are basically interchangeable. In this sentence, navečer fits well because the speaker is talking about a usual evening habit.

Also, it is written as one word: navečer.

Semantically, se belongs with prekriti: prekriti se = to cover oneself.

But in Croatian, short words like se are clitics, and clitics usually go very early in the clause, often in second position. Since navečer comes first in that part of the sentence, se comes right after it:

navečer se volim prekriti

If the clause started with volim, you would normally get:

Volim se prekriti toplim poplunom.

What you usually do not want in standard Croatian is volim prekriti se.

Here volim prekriti se means I like to cover myself or I enjoy covering myself.

So volim does not have to mean strong emotional love. With an infinitive, it often expresses a preference, habit, or something someone likes doing.

Prekriti se means to cover oneself, especially by pulling something over your body, like a blanket or duvet.

In this sentence, it means the speaker likes to cover up with a warm duvet when it gets cold.

Prekriti is a perfective infinitive. That means it presents the action as a whole, completed act: to cover oneself up.

That works well here because the sentence describes a typical thing the speaker likes to do in that situation. An imperfective form such as prekrivati se would focus more on the process or repeated ongoing action and would sound less natural here.

Because after prekriti se, the thing you use to cover yourself is in the instrumental case.

So:

• topao poplun = a warm duvet
• toplim poplunom = with a warm duvet

Both words change:

• topao → toplim
• poplun → poplunom

It is instrumental singular.

This is a very common use of the instrumental in Croatian: it marks the means or the thing used to do something. Here, the duvet is what the speaker uses to cover themself.

A poplun is a duvet, comforter, or sometimes quilt, depending on the variety of English.

It is not quite the same as deka, which is a blanket. So topli poplun suggests a thicker bed covering.

Croatian often leaves out subject pronouns when they are already clear from the verb ending.

The form volim already tells you the subject is I. So ja is unnecessary unless you want extra emphasis or contrast.

For example:

• Volim se prekriti toplim poplunom. = neutral
• Ja se volim prekriti toplim poplunom. = more emphatic

Yes, Croatian word order is fairly flexible, although clitics like se still have placement rules.

For example, these are possible:

• Kad zahladi, navečer se volim prekriti toplim poplunom.
• Kad zahladi, volim se navečer prekriti toplim poplunom.
• Navečer se volim prekriti toplim poplunom kad zahladi.

The basic meaning stays similar, but the emphasis changes a little. The original sentence sounds natural and balanced.

Because Kad zahladi is a subordinate clause placed before the main clause.

In Croatian, when a subordinate clause comes first, it is normally separated from the main clause by a comma: Kad zahladi, navečer se volim prekriti toplim poplunom.

So the comma here is standard and expected.