Kad je temperatura visoka, pijem više vode.

Kad means when here.

In Croatian, kad and kada usually mean the same thing. The difference is mostly style:

• kad = a little more common in everyday speech
• kada = often felt as slightly more formal or more neutral in careful writing

So this sentence could also be:

• Kada je temperatura visoka, pijem više vode.

Both are correct.

Je is the 3rd person singular present form of biti = to be.

So:

• temperatura je visoka = the temperature is high

In the full sentence, je connects the subject temperatura with the adjective visoka.

Because visoka has to agree with temperatura.

Temperatura is:

• feminine
• singular
• nominative

So the adjective must match it:

• visok = basic dictionary form, masculine
• visoka = feminine singular
• visoko = neuter singular

That is why you get:

• temperatura je visoka

not visok or visoko.

Because temperatura is the subject of the clause, so it is in the nominative case.

Compare:

• Temperatura je visoka. = The temperature is high.

  • subject → nominative → temperatura

• Mjerim temperaturu. = I am measuring the temperature.

  • direct object → accusative → temperaturu

So in your sentence, temperatura is not something being acted on; it is the thing that is high.

Pijem is the 1st person singular present tense of piti = to drink.

So:

• pijem = I drink / I am drinking

In this sentence, it is best understood as a habitual or general present:

• When the temperature is high, I drink more water.

Croatian often uses the present tense this way for regular behavior or general truths.

Because Croatian usually leaves out subject pronouns when they are already clear from the verb form.

• pijem already tells you the subject is I
• so ja is not necessary

You could say:

• Kad je temperatura visoka, ja pijem više vode.

But that usually adds emphasis, as if you are contrasting yourself with someone else.

Because after više meaning more, the noun normally goes into the genitive.

With voda = water, that gives:

• nominative: voda
• genitive singular: vode

So:

• više vode = more water

This is especially common with mass nouns like:

• voda = water
• mlijeko = milk
• kava = coffee

Examples:

• Pijem više kave. = I drink more coffee.
• Trebamo više mlijeka. = We need more milk.

Here više functions as a quantity word meaning more.

It is related to the comparative form of mnogo / puno in meaning, but in practice learners often just remember:

• više + genitive noun = more + noun

So in:

• pijem više vode

više is not describing vode like an ordinary adjective would. It is expressing a greater quantity of water.

Yes. Croatian word order is fairly flexible.

Your sentence:

• Kad je temperatura visoka, pijem više vode.

could also be:

• Pijem više vode kad je temperatura visoka.

Both are natural. The difference is mainly in emphasis:

• starting with Kad je temperatura visoka emphasizes the condition/time frame first
• starting with Pijem više vode emphasizes the main action first

Because the sentence begins with a subordinate clause:

• Kad je temperatura visoka = when the temperature is high

Then comes the main clause:

• pijem više vode = I drink more water

When the subordinate clause comes first, Croatian normally separates it with a comma:

• Kad je temperatura visoka, pijem više vode.

If the main clause comes first, you usually do not put a comma before kad in a simple sentence like this:

• Pijem više vode kad je temperatura visoka.

Usually it means a general or repeated situation:

• When the temperature is high, I drink more water.

That is, whenever it is hot or the temperature is high, this is what I do.

Croatian present tense often covers this kind of habitual meaning without needing a special form.

If you wanted to talk about one specific past situation, Croatian would normally use past tense forms instead.

The sentence is correct, but in everyday speech many people might say something simpler and more natural, such as:

• Kad je vruće, pijem više vode. = When it’s hot, I drink more water.

Your original sentence sounds a bit more explicit or slightly more formal because it talks about temperature directly.

So:

• Kad je temperatura visoka... = correct, understandable, a bit more formal/explicit
• Kad je vruće... = very common in everyday speech

A rough pronunciation guide is:

Kad ye tem-pe-ra-TOO-ra vee-SO-ka, PEE-yem VEE-she VO-deh.

A few useful points:

• j is pronounced like English y in yes
• š sounds like sh
• c in vode is not present here, so that word is simple: vo-de
• stress in Croatian is not always easy to predict, so it is best learned by listening as well as reading

Here are the main forms:

• kad = when
• biti → je = to be → is
• temperatura = temperature
• visok → visoka = high
• piti → pijem = to drink → I drink
• više = more
• voda → vode = water → of water / water after više

This is a useful habit in Croatian: when you meet a sentence, try to identify the dictionary form of each word and then the form actually used in context.