Veðurspáin segir að veðrið verði betra á morgun.

The base noun is veðurspá, which means weather forecast.

In Icelandic, the definite article is often attached to the end of the noun instead of being a separate word like English the. So:

• veðurspá = weather forecast
• veðurspáin = the weather forecast

Here, -in is the definite ending for this feminine noun in the nominative singular.

Yes. Segir is the 3rd person singular present of segja = to say.

Just like in English, Icelandic can use say with things like reports, signs, forecasts, and statistics:

• Veðurspáin segir ... = The weather forecast says ...

In natural English, you might also translate it as:

• The forecast says ...
• The forecast predicts ...
• The forecast indicates ...

So segir is completely normal here.

Að here means that and introduces a subordinate clause:

• Veðurspáin segir að ...
• The weather forecast says that ...

English often drops that, but Icelandic commonly keeps að in this kind of sentence.

So the structure is:

• main clause: Veðurspáin segir
• subordinate clause: að veðrið verði betra á morgun

Because Icelandic word order changes between main clauses and subordinate clauses.

In main clauses, Icelandic usually follows the verb-second rule.
But after a subordinating word like að, that rule normally does not apply in the same way.

So the neutral order in the subordinate clause is:

• veðrið = subject
• verði = verb
• betra = complement

That gives:

• að veðrið verði betra

For a learner, this is the normal pattern to expect after að.

Verði is the subjunctive form of verða.

In Icelandic, the subjunctive is very common in subordinate clauses that report what someone says, thinks, hopes, predicts, or believes, especially when the speaker is not presenting the content as a firm fact.

So here:

• verður = indicative
• verði = subjunctive

Because this is a reported prediction from the forecast, verði is very natural.

Not exactly. Icelandic does not have a special future tense ending like some languages do.

Instead, future meaning is often shown by:

• context
• time words such as á morgun = tomorrow
• sometimes verbs like verða

So in this sentence, the future meaning comes from the whole expression:

• veðrið verði betra á morgun = the weather will be better tomorrow

Even though verði is not a special future-tense form, the sentence clearly refers to the future.

They are all in forms that match their roles in the sentence:

• veðurspáin is nominative singular because it is the subject of the main clause
• veðrið is nominative singular because it is the subject of the subordinate clause
• betra is a predicate adjective and agrees with veðrið

Because veðrið is neuter singular, the adjective must also be neuter singular, which is why it is betra.

Betra is the comparative form meaning better, and it agrees with veðrið.

The adjective comes from góður = good, which is irregular, just like English:

• good → better
• góður → betri / betra

Since veður is a neuter noun, the correct form here is betra.

So:

• veðrið verði betra = the weather will be better

Veðrið means the weather, while veður means weather in a more general sense.

In Icelandic, when talking about the specific weather in question, especially in everyday speech and forecasts, the definite form is very common:

• veður = weather in general
• veðrið = the weather, the weather conditions we are talking about

So in this sentence, the forecast is talking about a particular set of weather conditions, which is why veðrið sounds natural.

Á morgun means tomorrow.

Even though á often means on, here the whole phrase works as a fixed time expression. It is best learned as a unit:

• á morgun = tomorrow

This is one of those places where Icelandic uses a preposition in a way that English does not. So it is better not to translate it word-for-word, but simply remember the phrase as the normal Icelandic way to say tomorrow.

A little of all three, depending on how naturally you want to translate it.

Literally, verða betra is close to:

• become better
• get better

But in English, with weather forecasts, we often simply say:

• the weather will be better

So all of these are connected:

• veðrið verður betra = the weather gets better / becomes better / will be better

In this sentence, the smoothest English translation is usually will be better, even though the Icelandic verb still has that underlying sense of become / get.