Svona skýrt veður er sjaldgæft á þessum tíma árs.

Here svona means something like such, this kind of, or like this.

So svona skýrt veður means such clear weather or weather this clear.

A useful thing to know is that svona is very common in everyday Icelandic and can be used a bit broadly:

• svona dagur = a day like this
• svona stórt hús = such a big house
• Ekki gera svona. = Don’t do that / Don’t act like that

In this sentence, it is describing the kind or degree of weather.

Because veður is a neuter noun, and the adjective has to agree with it.

The adjective skýr changes form depending on gender, number, and case. In the nominative singular:

• masculine: skýr
• feminine: skýr
• neuter: skýrt

Since veður is neuter singular, you need skýrt.

So:

• skýrt veður = clear weather

This kind of adjective agreement is very important in Icelandic.

Yes, veður is a neuter noun.

In Icelandic, noun gender is grammatical, so it is something you usually have to learn along with the word. One clue is the article form:

• veðrið = the weather

The ending -ið is a typical neuter singular definite ending.

Also, adjectives agreeing with veður appear in neuter:

• gott veður = good weather
• slæmt veður = bad weather
• skýrt veður = clear weather

So in this sentence, both skýrt and sjaldgæft show that the noun is neuter singular.

For the same reason as skýrt: it agrees with veður.

Sjaldgæfur means rare, and in nominative singular it changes like this:

• masculine: sjaldgæfur
• feminine: sjaldgæf
• neuter: sjaldgæft

Since the subject is svona skýrt veður, and the head noun veður is neuter singular, the predicate adjective also has to be neuter singular:

• Svona skýrt veður er sjaldgæft.

That is exactly parallel to sentences like:

• Veðrið er gott. = The weather is good.
• Húsið er stórt. = The house is big.

Because Icelandic does not have a separate indefinite article like English a/an.

So:

• veður can mean weather or a weather condition, depending on context
• skýrt veður = clear weather
• svona skýrt veður = such clear weather

Icelandic does have a definite article, but it is usually attached to the end of the noun:

• veður = weather
• veðrið = the weather

So the lack of a is completely normal.

This is a very common Icelandic time expression. It means at this time of year.

Here is the structure:

• á = at/on
• þessum tíma = this time
• árs = of year

More literally, it is:

• at this time of year

The noun tími is in the dative after á here:

• á þessum tíma

Then árs is the genitive singular of ár and means of year:

• tími árs = time of year

So the whole phrase is a fixed, natural Icelandic way to say at this time of year.

Because the preposition á takes the dative here.

The basic nominative form is:

• þessi tími = this time

But after á in this expression, Icelandic uses dative:

• á þessum tíma = at this time

Both the pronoun/determiner and the noun change:

• þessi → þessum
• tími → tíma

This is one of the big things English speakers have to get used to in Icelandic: prepositions often require a particular case.

Because árs is the genitive singular of ár.

The phrase means time of year, and in Icelandic that of year relationship is usually shown with the genitive:

• tími árs = time of year

So:

• ár = nominative form, year
• árs = genitive form, of year

This is very similar in function to English of year, but Icelandic often expresses it just by changing the noun’s ending rather than using a separate word like of.

Because the subject is understood as a singular noun phrase headed by veður.

The full subject is:

• Svona skýrt veður

The main noun there is veður, which is singular, so the verb is singular:

• er = is

Even though English weather is often treated as an uncountable noun, Icelandic still uses normal singular agreement here.

This is the most neutral, straightforward word order:

• subject: Svona skýrt veður
• verb: er
• complement: sjaldgæft
• time phrase: á þessum tíma árs

So it works like:

• Such clear weather is rare at this time of year.

Icelandic does allow other word orders for emphasis, especially because it is a V2 language, but this version is the plain, natural one for a statement.

For example, you might also see fronting for emphasis in other contexts, but for a learner, this sentence is best understood as standard subject-first word order.

In this sentence it means clear weather.

The word veður means weather, not sky. So skýrt veður refers to weather conditions being clear, typically with little cloud, good visibility, and no bad weather.

If you wanted to talk specifically about the sky, you would usually use a different noun, such as himinn:

• Heiður himinn or other expressions about the sky itself, depending on context

So here the focus is definitely on the weather, not literally the sky as an object.

Yes, it is a common and useful word, and rare is a good translation.

Sjaldgæfur is built from:

• sjald- related to seldom / infrequent
• gæfur

For learning purposes, it is best just to memorize sjaldgæfur as rare.

Examples:

• Þetta er sjaldgæft. = This is rare.
• Sjaldgæfir fuglar = rare birds
• Svona skýrt veður er sjaldgæft. = Such clear weather is rare.

It is a standard adjective and behaves normally in agreement.

Yes. Á þessum árstíma is also natural and means essentially the same thing: at this time of year.

You can think of these as two closely related ways to express the same idea:

• á þessum tíma árs
• á þessum árstíma

The version in your sentence is slightly more literally at this time of the year, while árstími is a compound noun meaning time of year / season-related time. Both are good Icelandic.

For a learner, it is useful to recognize both, even if you only actively use one at first.