Ako se do podneva ne razvedri, nećemo ići na izlet do jezera.

In Croatian, after ako (if), you normally use the present tense, even when the meaning is future.

So Croatian says literally something like:

If it doesn’t clear up by noon, we will not go...

not

If it will not clear up...

That is very similar to English, which also usually says If it doesn’t clear up, not If it won’t clear up.

Here, ne razvedri is present tense, but because it is inside an if-clause, it refers to a possible future situation.

Se is a reflexive particle, but in many verbs it does not translate literally as oneself. It is simply part of the verb.

Here the verb is:

razvedriti se = to clear up / to become clear

This is how Croatian expresses the weather becoming clearer. So:

• razvedriti se = the sky/weather clears up
• ne razvedri se / se ne razvedri = it doesn’t clear up

In this sentence, se is not optional. You need it because the normal weather expression is razvedriti se.

Because se is a clitic, and Croatian clitics usually go in a fixed position near the beginning of the clause.

Also, ne goes directly with the verb:

• ne razvedri

So the structure is:

• Ako = if
• se = clitic
• do podneva = by noon
• ne razvedri = does not clear up

You cannot normally say ne se razvedri.

The standard order is:

Ako se do podneva ne razvedri...

Croatian word order is somewhat flexible, but clitics like se follow special placement rules.

Nećemo ići is the normal way to express the future negative:

• ćemo ići = we will go
• nećemo ići = we will not go

Croatian forms the future with:

• present of htjeti (ću, ćeš, će...)
• • infinitive

So:

• ići ćemo = we will go
• nećemo ići = we will not go

In the negative, the auxiliary and negation are written together:

• neću, nećeš, neće, nećemo, nećete, neće

By contrast, ne idemo usually means we are not going / we do not go, not specifically we will not go.

Because future tense in Croatian is built with the auxiliary htjeti plus the infinitive of the main verb.

Here:

• nećemo = we will not
• ići = go

Together:

nećemo ići = we will not go

This is a standard future construction.

Na izlet uses the preposition na with the accusative case, because it expresses movement to an event or activity.

So:

• izlet = nominative
• na izlet = accusative

This is a common pattern:

• ići na posao = to go to work
• ići na ručak = to go to lunch
• ići na izlet = to go on an outing / excursion

So Croatian treats izlet as the destination/activity you are going to.

It is the same preposition, do, but the meaning changes slightly depending on context.

1. do podneva

Here it means by / until noon.

• do podneva = by noon / until noon

This is a time expression.

2. do jezera

Here it means to / as far as the lake.

• izlet do jezera = an outing to the lake

This is a place/destination expression.

So do basically suggests a limit or endpoint, but in English that may come out as:

• by / until for time
• to / as far as for place

In both uses, do requires the genitive case.

Because the preposition do takes the genitive case.

So:

• podne → do podneva
• jezero → do jezera

That is why the endings change.

You can think of it this way:

• nominative: podne, jezero
• genitive after do: podneva, jezera

This is a very common thing in Croatian: prepositions often require a specific case.

In this sentence, English would most naturally say by noon:

If it doesn’t clear up by noon, we won’t go...

But do podneva can feel close to until noon in a literal sense, because it marks the time limit up to noon.

So the practical meaning is:

• between now and noon, if the weather does not improve

In many contexts, by noon is the best English match.

Razvedriti se is a perfective verb.

That matters because Croatian often uses a perfective present form in subordinate clauses to refer to a completed future event, especially after words like ako.

So ne razvedri here means:

• it does not clear up
• it fails to become clear

The focus is on whether that change happens or not.

If you compare it with an imperfective weather verb, the nuance would be different. Perfective is very natural here because the sentence is about the result: Will the weather clear up by noon or not?

The word order is somewhat flexible, but not completely free.

The given sentence is very natural:

Ako se do podneva ne razvedri, nećemo ići na izlet do jezera.

You could also say:

Nećemo ići na izlet do jezera ako se do podneva ne razvedri.

That is also correct. The difference is mostly one of emphasis and style.

What is less flexible is the placement of clitics like se, and the fact that ne stays with the verb:

• se
• ne razvedri

So you can move larger chunks around, but you cannot place everything randomly.

Yes, literally do jezera often means to the lake / as far as the lake. In this sentence, with izlet, it naturally means the outing’s destination is the lake.

So:

• izlet do jezera = a trip/outing to the lake

It does not necessarily mean you are going into the lake area in a very precise grammatical sense; it just identifies the destination in a normal, idiomatic way.

Croatian often uses do for this kind of endpoint/destination idea.

Yes, that is quite close and helpful for understanding the structure:

• na izlet = on an outing / on a trip
• do jezera = to the lake

So literally:

to go on an outing to the lake

That said, in smoother English you might simply say:

• go on a trip to the lake
• go to the lake for an outing
• go on a lake trip

But grammatically, on an outing to the lake is a good way to see how the Croatian sentence is built.