Ako bude sunce, sutra ćemo biti na plaži od jutra do večeri.

In Serbian, after ako when you talk about a future condition, you normally do not use će in that clause.

So Serbian says:

• Ako bude sunce...
• literally: If there is sun / if it turns out sunny...

Using Ako će biti sunce sounds wrong or at least very unnatural in standard Serbian.

This is similar to English, where we say If it is sunny tomorrow..., not If it will be sunny tomorrow...

That is a very common question.

Serbian biti has two sets of forms that learners notice early:

• sam, si, je, smo, ste, su
  These are the usual present/auxiliary forms.
• budem, budeš, bude, budemo, budete, budu
  These are full verb forms used in certain constructions, especially in future-related and conditional contexts.

Here, bude is the 3rd person singular form from that second set.

So:

• On je ovde. = He is here.
• Ako bude ovde sutra... = If he is here tomorrow...

In your sentence, bude is exactly the form Serbian needs after ako for this kind of future condition.

Yes. It is normal.

Sunce here is a noun, and the phrase means something like:

• if there is sun
• if it’s sunny
• if the weather is sunny

A native speaker might also say:

• Ako bude sunčano... = If it’s sunny...
• Ako bude lepo vreme... = If the weather is nice...

So Ako bude sunce is a natural weather expression, even though English usually uses an adjective: sunny.

Because Serbian often leaves out subject pronouns when the verb already shows who the subject is.

In ćemo biti, the form ćemo already tells you the subject is we.

So:

• Sutra ćemo biti na plaži. = Tomorrow we’ll be at the beach.

You can add mi if you want emphasis or contrast:

• Mi ćemo biti na plaži, a oni kod kuće.
  = We’ll be at the beach, and they’ll be at home.

But in a neutral sentence, leaving out mi is completely normal.

The neutral Serbian word order prefers the clitic ćemo near the beginning of the clause, usually in second position.

That is why sutra ćemo biti sounds very natural.

• Sutra ćemo biti na plaži. = neutral, standard

A form with bićemo is also possible, but it usually works better when it starts the clause or appears in a different rhythm:

• Bićemo na plaži sutra.
• Bićemo sutra na plaži.

But Sutra bićemo... sounds marked and less natural to most speakers.

Plaži is locative singular.

The preposition na can mean on or at, and with location it often takes the locative.

So:

• na plaži = at/on the beach

This is just the normal Serbian way to express location with plaža.

Compare:

• na stolu = on the table
• na poslu = at work
• na moru = at the seaside / at the sea
• na plaži = on the beach

Both od and do take the genitive.

So in this phrase:

• od jutra = from morning
• do večeri = until evening

That means:

• jutra is genitive singular of jutro
• večeri is genitive singular in this expression

The whole phrase means:

• from morning till evening
• all day long

It is a very common time expression in Serbian.

This is mostly something you should learn as a set phrase.

In everyday learning, you usually first meet veče for evening, but Serbian also preserves forms like večer / večeri in certain expressions.

That is why you often hear:

• do večeri
• tokom večeri
• od jutra do večeri

So the safest approach is to memorize od jutra do večeri as a chunk.

The sentence can be rearranged.

For example, you can also say:

• Sutra ćemo biti na plaži ako bude sunce.

That means the same thing.

The version with the if-clause first:

• Ako bude sunce, sutra ćemo biti na plaži od jutra do večeri.

puts more emphasis on the condition.

The version with the main clause first:

• Sutra ćemo biti na plaži ako bude sunce.

starts with the main idea and adds the condition after it.

Because Serbian has no articles.

So na plaži can mean:

• on the beach
• at the beach
• sometimes even on a beach

The exact meaning comes from context.

If you need to make it more specific, Serbian uses other words, for example:

• na toj plaži = on that beach
• na jednoj plaži = on a beach / on one beach

So English speakers often look for the, but Serbian simply does not use articles.

Yes, you could.

• od jutra do večeri = from morning till evening
• ceo dan = all day

So a natural alternative would be:

• Ako bude sunce, sutra ćemo ceo dan biti na plaži.

The original sentence is a bit more vivid because it spells out the time span: from morning to evening.