Poslije kiše ostane velika vlaga u zraku, pa mi je u stanu pretoplo.

Because poslije requires the genitive case.

• basic form: kiša = rain
• genitive singular: kiše

So:

• poslije kiše = after the rain / after rain

This is very common in Croatian. Another similar preposition is nakon, which also takes the genitive:

• nakon kiše

Almost yes. Both mean after and both take the genitive.

So both of these are correct:

• poslije kiše
• nakon kiše

In many situations they are interchangeable. Poslije often feels a bit more everyday and conversational, while nakon can sound slightly more neutral or formal, but the difference is small.

Ostane comes from the verb ostati, which means to remain, to stay, or to be left.

Here it means something like:

• a lot of humidity remains in the air
• a lot of humidity is left in the air

Grammatically, ostane is 3rd person singular.

The form is from a perfective verb, so it highlights the result after the rain: once the rain is over, humidity is left behind.

This is a very natural question, because both forms can look possible.

• ostaje = imperfective, more like remains / is remaining
• ostane = perfective, more like ends up remaining / is left behind

In this sentence, ostane focuses on the result of the rain: after it rains, humidity is left in the air. That perfective feel is very natural in everyday Croatian when talking about a typical result of something.

If you used ostaje, the meaning would be close, but the nuance would be a bit more about the ongoing state rather than the resulting outcome.

Because vlaga is the subject of ostane, so it is in the nominative case.

• vlaga = humidity
• velika = big / high / great

The adjective must agree with the noun:

• vlaga is feminine singular
• so the adjective is also feminine singular nominative: velika

So:

• velika vlaga = high humidity / a lot of humidity

Because u means in, and when it shows location, it usually takes the locative case.

So:

• zrak = air
• u zraku = in the air

and:

• stan = apartment / flat
• u stanu = in the apartment

A very useful contrast is:

• u stanu = in the apartment → location, so locative
• u stan = into the apartment → movement, so accusative

Here there is no movement, only location, so zraku and stanu are in the locative.

Here pa means something like:

• so
• and so
• therefore

It connects the first clause to the consequence in the second clause:

• humidity stays in the air,
• so it is too warm for me in the apartment.

In other contexts, pa can also mean something closer to and then, depending on the sentence.

Mi is the dative form of ja, and here it means to me or for me.

So:

• mi je pretoplo = it is too warm for me

This is a very common Croatian pattern for physical sensations, comfort, and personal experience:

• Hladno mi je. = I am cold.
• Vruće mi je. = I am hot.
• Dobro mi je. = I feel good.
• Pretoplo mi je. = It is too warm for me.

English often uses I am..., but Croatian often uses dative pronoun + je + adjective/adverb.

Toplo means warm.

The prefix pre- often means too or excessively.

So:

• toplo = warm
• pretoplo = too warm

This is very common in Croatian:

• prehladno = too cold
• preskupo = too expensive
• previše = too much

So pre- is a very useful prefix to learn.

Because Croatian does not have articles like English a and the.

So Croatian simply says:

• u zraku = in the air
• u stanu = in the apartment / in an apartment

Whether it means the or an is understood from context.

That is why English speakers often feel something is missing at first, but in Croatian this is completely normal.

Because there are two clauses here:

• Poslije kiše ostane velika vlaga u zraku
• pa mi je u stanu pretoplo

In Croatian, when clauses are joined with words like pa, a comma is commonly used. It helps show the pause and the logical connection between the two parts.

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

The original sentence is natural, but other versions are also possible, for example:

• Poslije kiše velika vlaga ostane u zraku, pa mi je u stanu pretoplo.
• Poslije kiše ostane velika vlaga u zraku, pa je meni u stanu pretoplo.
• Poslije kiše ostane velika vlaga u zraku, pa mi je pretoplo u stanu.

The basic meaning stays similar, but the emphasis changes.

In the original sentence, u stanu comes before pretoplo, which helps set up the location before giving the feeling: in the apartment, it is too warm for me.