Vani puše jak vjetar.

Vani means outside or outdoors.

It is an adverb, not a noun or a preposition. That means it does not require a case ending after it in this sentence. It simply tells you where the action is happening.

So:

• vani = outside
• unutra = inside

Puše is the 3rd person singular present tense of the verb puhati = to blow.

So it can mean:

• blows
• is blowing

Croatian does not usually make the same clear grammatical distinction that English does between blows and is blowing. The context tells you which meaning is intended.

The subject is jak vjetar.

More specifically:

• vjetar = wind
• jak = strong

So vjetar is the noun, and jak describes it.

Literally, the structure is close to:

• Outside blows strong wind

But English normally says:

• A strong wind is blowing outside

This is a very common question.

Here, jak is the masculine singular nominative form used with vjetar. In standard Croatian, jak vjetar is the normal, natural choice for a general descriptive meaning like a strong wind.

You may also see jaki vjetar, but that form can sound more definite, more specific, or sometimes just reflect another style of usage. For a learner, the safest choice in a sentence like this is:

• jak vjetar = a strong wind

Also notice that the adjective agrees with the noun:

• jak = masculine singular nominative
• vjetar = masculine singular nominative

Because Croatian has no articles.

English says:

• a strong wind
• the strong wind

Croatian usually just says:

• jak vjetar

The listener understands from context whether it means a strong wind, the strong wind, or simply strong wind in a general sense.

Croatian word order is much more flexible than English word order.

This sentence starts with Vani to set the scene first: Outside...

Then comes the verb:

• puše = is blowing

Then the subject:

• jak vjetar = a strong wind

This order sounds natural when you are describing what is happening in the environment.

Other orders are possible too, for example:

• Jak vjetar puše vani.
• Vani jak vjetar puše.

But they may sound a bit different in emphasis. Vani puše jak vjetar is a very natural way to present the situation.

No. Croatian does not use a dummy subject like English it.

In English, you say:

• It is raining
• It is windy

Croatian does not need that kind of it.

For example:

• Pada kiša. = It is raining.
• Puše vjetar. = The wind is blowing.

In your sentence, there is a real subject anyway:

• vjetar = wind

So there is no need for anything like English it.

Vjetar is in the nominative singular because it is the subject of the sentence.

That is also why the adjective matches it:

• jak = nominative singular masculine
• vjetar = nominative singular masculine

Croatian adjectives agree with the nouns they describe in:

• gender
• number
• case

A rough guide for an English speaker:

• puše ≈ POO-sheh
• vjetar ≈ VYEH-tar

A few details:

• š sounds like sh in shoe
• j sounds like y in yes
• the r in vjetar is a tapped or rolled Croatian r

So:

• puše = POO-sheh
• vjetar = VYEH-tar

Yes. Jak is very common with weather and natural force.

Examples:

• jak vjetar = strong wind
• jaka kiša = heavy/strong rain
• jako sunce = strong sun

You might also hear snažan vjetar, which also means strong wind, but jak vjetar is very common and natural.

It can do both, depending on context.

Because puše is present tense, it may mean:

• A strong wind is blowing outside right now
• A strong wind blows outside / It is windy outside in a more general sense

In real use, context usually makes it clear. If someone says it while looking out the window, it almost certainly means something happening right now.