Kada pada sneg, meni treba jakna.

Yes. Serbian often expresses it is snowing as pada sneg, literally snow is falling.

• pada = falls / is falling
• sneg = snow

So Kada pada sneg means When it snows or more literally When snow falls.

A very common alternative is Kad sneži, which also means When it snows.

Kada means when.

It introduces a time clause:

• Kada pada sneg = When it snows

In everyday speech, kad is very common instead of kada:

• Kad pada sneg, meni treba jakna.

Both are correct. Kada can sound a bit more neutral or slightly more formal.

The comma separates the subordinate clause from the main clause.

• Kada pada sneg = subordinate time clause
• meni treba jakna = main clause

This is similar to English:

• When it snows, I need a jacket.

So the comma is normal and expected here.

In Serbian, trebati is very often used in an impersonal-style structure for to need:

• Meni treba jakna.
• literally: To me, a jacket is needed.
• natural English: I need a jacket.

This is one of the most important things for English speakers to notice. Serbian often says X is needed to me instead of using I need X with a direct-object structure.

So:

• meni = to me
• treba = is needed
• jakna = a jacket

The sentence is completely natural Serbian.

Because meni is the dative form of ja.

With this use of trebati, the person who needs something is put in the dative:

• ja = I
• meni = to me

So:

• Meni treba jakna. = I need a jacket.

A shorter clitic form is also possible:

• Treba mi jakna.

That is probably the most common everyday word order.

Both mean to me, but they are used differently.

• mi = short unstressed clitic form
• meni = full stressed form

Compare:

• Treba mi jakna. = neutral, very common
• Meni treba jakna. = more emphasis on me
• Meni treba jakna, a njemu kaput. = I need a jacket, and he needs a coat.

So in your sentence, meni may sound slightly more emphatic or contrastive, though it is still perfectly normal.

With this Serbian pattern, jakna is treated as the grammatical subject of treba, not as a direct object.

That is why it appears in the nominative:

• jakna = nominative singular

Think of it like this:

• Meni treba jakna.
• literally: A jacket is needed to me.

Because jakna is the thing that is needed, it stands in nominative and controls the verb form.

Because it agrees with jakna, which is singular.

• jakna = singular feminine noun
• therefore treba = singular form

If the thing needed were plural, the verb would usually be plural too:

• Meni trebaju rukavice. = I need gloves.

You may also hear treba rukavice in some real-life usage, but for learners, it is best first to understand the agreement pattern:

• singular noun -> treba
• plural noun -> trebaju

Yes, absolutely. Treba mi jakna is very natural and probably the most everyday way to say it.

All of these are possible:

• Treba mi jakna.
• Meni treba jakna.
• Jakna mi treba. (more emphasis on jacket)

The meaning stays basically the same, but the emphasis changes.

No. A very common alternative is:

• Kad sneži

So you could say:

• Kad sneži, treba mi jakna.

Both are natural. The difference is mainly stylistic:

• pada sneg = literally snow falls
• sneži = it is snowing

A learner should understand both.

In this sentence, jakna can often be understood as a jacket in English, but Serbian does not have articles like a and the.

So jakna by itself can mean:

• a jacket
• the jacket

The exact meaning depends on context.

In Meni treba jakna, English usually translates it as I need a jacket, because that sounds most natural.

Yes. Serbian word order is flexible, though not completely random. Different orders change emphasis more than basic meaning.

Possible versions include:

• Kada pada sneg, meni treba jakna.
• Kada pada sneg, treba mi jakna.
• Treba mi jakna kada pada sneg.

These all mean roughly When it snows, I need a jacket, but the first puts the time clause first, while others may sound more conversational or shift focus.

Usually it sounds general:

• When it snows, I need a jacket.

That is, whenever that situation happens, a jacket is necessary.

If the context were specific, it could also refer to a particular occasion, but without extra context, learners should read it as a general statement.