Το βράδυ στο μπαλκόνι έχει ωραίο αεράκι.

In everyday Greek, έχει is often used impersonally to mean there is / there are, especially in spoken language.

So:

• Έχει ωραίο αεράκι. = There is a nice breeze.

This is very common and natural in speech.
A more formal or bookish option would be υπάρχει, but that is not what people usually say in simple everyday sentences like this.

Compare:

• Έχει κόσμο εδώ. = There are people here.
• Έχει πρόβλημα. = There is a problem.

So in this sentence, έχει does not mean that someone has a breeze.

Το βράδυ is a very common time expression meaning in the evening / at night, depending on context.

It is a fixed and natural way to say when something happens.

Examples:

• Το πρωί = in the morning
• Το μεσημέρι = at noon / in the midday
• Το απόγευμα = in the afternoon
• Το βράδυ = in the evening / at night

This use of the article + noun is an adverbial time expression. Greek does this a lot.

As for the alternatives:

• στη βραδιά is not the normal way to say this
• τη νύχτα means at night / during the night, but it is slightly different in feel from το βράδυ

Very roughly:

• το βράδυ = evening, or the night period as part of the daily routine
• τη νύχτα = nighttime, often later and darker, sometimes more literary or specific

Στο is a contraction of:

• σε = in / at / on / to
• το = the

So:

• σε + το = στο

Therefore:

• στο μπαλκόνι = on the balcony / at the balcony

The noun μπαλκόνι is neuter, which is why it takes το.

Other examples of the same pattern:

• στο σπίτι = in the house / at home
• στο τραπέζι = on the table
• στο δωμάτιο = in the room

Greek often leaves out the indefinite article in cases where English would naturally say a.

So:

• έχει ωραίο αεράκι literally looks like it has nice little-breeze
• but naturally it means there is a nice breeze

You could also say:

• έχει ένα ωραίο αεράκι

That means almost the same thing, but ένα makes it a bit more explicitly a certain / a nice breeze.

Without ένα, the phrase still sounds completely natural and often a little smoother.

Αεράκι is the diminutive form of αέρας.

• αέρας = air / wind
• αεράκι = little breeze / gentle breeze

The ending -άκι is a very common diminutive ending in Greek. It often suggests something:

• small
• light
• pleasant
• affectionate
• less intense

So αεράκι is not just wind. It usually gives the idea of a light, pleasant breeze.

That is why ωραίο αεράκι sounds very natural: it suggests a nice, refreshing little breeze.

Because αεράκι is a neuter singular noun.

Adjectives in Greek agree with the noun they describe in:

• gender
• number
• case

So:

• ωραίος = masculine singular
• ωραία = feminine singular
• ωραίο = neuter singular

Since αεράκι is neuter, the adjective must also be neuter:

• ωραίο αεράκι

After έχει, the noun functions like the direct object, so it is in the accusative.

So grammatically, ωραίο αεράκι is accusative.

However, with many neuter singular nouns, the nominative and accusative forms are the same, so you do not see a visible change here.

For example:

• nominative: το αεράκι
• accusative: το αεράκι

The article changes in some contexts, but the noun form itself stays the same.

The word order is not completely fixed. Greek allows more flexibility than English.

This sentence could be rearranged, for example:

• Το βράδυ στο μπαλκόνι έχει ωραίο αεράκι.
• Στο μπαλκόνι το βράδυ έχει ωραίο αεράκι.
• Έχει ωραίο αεράκι στο μπαλκόνι το βράδυ.

These all mean roughly the same thing, but the emphasis changes slightly.

The original order sounds natural because it sets the scene first:

1. Το βράδυ = when
2. στο μπαλκόνι = where
3. έχει ωραίο αεράκι = what the situation is

Yes, grammatically you could, and people would understand it. But in everyday Greek, έχει is much more common in this kind of sentence.

Compare the feel:

• Έχει ωραίο αεράκι. = very natural, everyday spoken Greek
• Υπάρχει ωραίο αεράκι. = understandable, but more formal or less idiomatic here

So if you want to sound natural in conversation, έχει is usually the better choice.

It can mean either, depending on context.

Greek βράδυ covers a time span that English may divide differently. In many situations, English might translate it as:

• in the evening
• at night
• tonight, in some contexts

So you should not expect a perfect one-to-one match with English.

In this sentence, the idea is simply that during the evening/night time, there is a nice breeze on the balcony.

Yes, it is natural and understandable.

It has a very conversational feel, especially because of:

• έχει used as there is
• αεράκι, which sounds vivid and pleasant

A speaker might also say:

• Το βράδυ στο μπαλκόνι έχει ένα ωραίο αεράκι.
• Το βράδυ στο μπαλκόνι φυσάει ωραίο αεράκι.

But your original sentence is perfectly normal Greek.

Greek often leaves out subject pronouns when they are not needed, because the verb form already gives enough information.

In this sentence, though, the bigger point is that έχει is being used impersonally. English often needs a dummy subject:

• There is a nice breeze
• sometimes English also uses it in weather-like expressions

Greek does not need that kind of placeholder here. It simply says:

• Έχει ωραίο αεράκι.

That is one reason Greek can feel more compact than English in sentences like this.