Ujutro je hladno.

In this sentence, ujutro is a fixed adverb meaning in the morning. As an adverb, it is normally written as one word.

So:

• Ujutro je hladno. = It is cold in the morning.

A learner might expect u jutro, because u often means in and jutro means morning, but here the usual expression is the single-word adverb ujutro.

Ujutro means in the morning or during the morning.

It usually gives a general time setting, not necessarily one specific morning. So this sentence often means something like:

• It’s cold in the morning
• Mornings are cold

If you want this morning, Serbian more often uses jutros:

• Jutros je hladno. = It is cold this morning.

Serbian often uses an impersonal construction for weather, temperature, and general conditions.

In English, you say:

• It is cold.

But that it does not really refer to anything. It is just a dummy subject.

In Serbian, you usually do not need such a subject. So you say:

• Hladno je. = It is cold.

Here, je is the 3rd person singular of biti (to be), even though there is no explicit subject.

This is a very common Serbian pattern. Je is a clitic, and clitics usually go in second position in the sentence or clause.

So:

• Ujutro je hladno.

The first element is ujutro, and then the clitic je comes right after it.

Compare:

• Hladno je.
• Danas je hladno.
• Ujutro je hladno.

A beginner might want to say Ujutro hladno je, but that is not the normal word order.

In this kind of impersonal sentence, Serbian normally uses the neuter singular form:

• hladno

That is why you say:

• Hladno je. = It is cold.

You use forms like hladan, hladna, or hladno when an adjective agrees with a noun:

• Dan je hladan. = The day is cold.
• Voda je hladna. = The water is cold.
• Jutro je hladno. = The morning is cold.

But in Ujutro je hladno, there is no noun for the adjective to agree with, so the impersonal neuter form hladno is used.

A learner may wonder about this because hladno can look like an adverb. In this sentence, it is best understood as the predicate form used in an impersonal sentence.

In practical terms, just learn:

• Hladno je = It is cold
• Toplo je = It is warm
• Vruće je = It is hot

So even if hladno can function adverbially in other contexts, here it is part of the standard way Serbian expresses a general condition like weather or temperature.

Yes, but the emphasis changes.

The neutral version is:

• Ujutro je hladno.

You can also say:

• Hladno je ujutro.

This still means It is cold in the morning, but now the focus is a bit more on cold.

What you generally cannot do in normal speech is place je freely anywhere you want. Because it is a clitic, it tends to stay in second position.

Usually, it sounds like a general statement:

• It’s cold in the morning
• In the mornings, it is cold

If you want to emphasize today’s morning, Serbian usually prefers:

• Jutros je hladno. = It is cold this morning.

So ujutro often feels more general or habitual, while jutros points to a specific morning.

You simply negate je:

• Ujutro nije hladno. = It is not cold in the morning.

So:

• je → nije

This is the normal way to negate this kind of sentence.

You change the form of biti (to be):

• Ujutro je hladno. = It is cold in the morning.
• Ujutro je bilo hladno. = It was cold in the morning.
• Ujutro će biti hladno. = It will be cold in the morning.

The word hladno stays the same; the tense is shown by the verb.

You could, but it does not mean exactly the same thing.

• Ujutro je hladno. = It is cold in the morning.
• Jutro je hladno. = The morning is cold.

The second sentence treats jutro as a noun (morning), so it sounds more literal and less like the usual time expression.

For the meaning in your sentence, ujutro is the natural choice.

No. Serbian has no articles.

So where English uses words like the and a, Serbian usually does not use anything equivalent.

That is why:

• Ujutro je hladno.

has no word corresponding to the or a. The meaning is understood from context.

You may hear ujutru in some varieties of Serbian, but ujutro is the safest standard form to learn and use.

So for a learner, the best choice is:

• Ujutro je hladno.