Þau taka pylsur og gos með sér út í garðinn þegar veðrið er gott.

Þau means they.

In Icelandic, þau is the third-person plural neuter form, but in real usage it often refers to:

• a mixed group of people
• a group of children
• people whose grammatical gender is not being specified individually

So in this sentence, þau taka... simply means they take...

In the present tense, Icelandic verbs do change by person, but the third-person plural form of taka is taka.

Here is the present tense of að taka:

• ég tek = I take
• þú tekur = you take
• hann/hún/það tekur = he/she/it takes
• við tökum = we take
• þið takið = you all take
• þeir/þær/þau taka = they take

So þau taka is the normal way to say they take.

Pylsur means hot dogs.

The singular is:

• pylsa = a hot dog

The plural is:

• pylsur = hot dogs

In this sentence, pylsur is the direct object of taka, and for this noun the nominative plural and accusative plural look the same: pylsur.

So:

• þau taka pylsur = they take hot dogs

Gos means soda, soft drink, or fizzy drink.

It is a neuter noun, and in the singular its form is often the same in nominative and accusative:

• gos = soda / a soft drink

So after taka, you still get:

• þau taka gos = they take soda / a soft drink

Depending on context, English might translate it as:

• soda
• soft drinks
• something to drink

Even though the Icelandic form is singular-looking, it can sometimes be understood more generally.

Með sér means with themselves / with them in a reflexive sense.

In this sentence:

• þau taka pylsur og gos með sér = they take hot dogs and soda with them

The important point is that sér is a reflexive pronoun. It refers back to the subject of the clause, here þau.

So:

• með sér = with themselves / with themself / with them, referring back to the subject

This is very common in Icelandic.

This is a very common learner question.

• með sér refers back to the subject of the sentence
• með þeim refers to some other people or things, not normally the subject itself

So in this sentence:

• Þau taka ... með sér = They take ... with them

That means the people doing the action are also the ones the phrase refers back to.

If you said:

• Þau taka ... með þeim

that would usually suggest with them = with some other people, not the same group as the subject.

So sér is used because the reference is reflexive.

Because this sentence expresses movement toward a place, not just location.

• í
  • accusative often shows motion into somewhere
• í
  • dative often shows being in a place

Here:

• garðinn is the accusative singular definite form of garður = garden
• út í garðinn means out into the garden

Compare:

• Þau fara út í garðinn = They go out into the garden
• Þau eru úti í garðinum = They are out in the garden

So:

• garðinn = motion into the garden
• garðinum = location in the garden

Út í means something like out into.

It combines:

• út = out
• í = into / in

Together, út í garðinn gives the idea of going or taking something out into the garden.

It is very natural Icelandic for movement from indoors or from one place outward into another space.

Veður means weather.

Veðrið means the weather.

Icelandic usually adds the definite article to the end of the noun, instead of using a separate word like English the.

So:

• veður = weather
• veðrið = the weather

In this sentence:

• þegar veðrið er gott = when the weather is good

Because gott agrees with veðrið, which is neuter singular.

The adjective góður = good changes form depending on gender, number, and case.

Here are the singular nominative forms:

• góður = masculine
• góð = feminine
• gott = neuter

Since veðrið is neuter singular, you need:

• veðrið er gott = the weather is good

Þegar means when in this sentence.

It introduces a time clause:

• þegar veðrið er gott = when the weather is good

So the whole sentence means that they do this when the weather is good.

A useful note: þegar can also mean when in questions about time, depending on context, but here it is a conjunction introducing a subordinate clause.

Because this is a subordinate clause, and Icelandic often keeps a normal subject-verb order there.

So:

• veðrið = subject
• er = is
• gott = good

This gives:

• þegar veðrið er gott = when the weather is good

Learners often notice that Icelandic main clauses have verb-second patterns, but subordinate clauses can look more straightforward.

Yes, very much.

Pylsur are famously associated with Icelandic food culture, and gos is a very everyday word for soda or soft drinks. So pylsur og gos sounds like a normal, natural picnic or outdoor-food combination.

That makes the whole sentence feel quite idiomatic:

• they take hot dogs and soda with them out into the garden when the weather is good

Yes. Depending on context, natural English translations could include:

• They take hot dogs and soda with them out into the garden when the weather is good.
• When the weather is good, they take hot dogs and soft drinks out into the garden with them.
• They bring hot dogs and soda out into the garden when the weather is nice.

A few notes:

• taka með sér can often sound like take with them or bring along
• gos might be translated as soda, soft drinks, or fizzy drinks
• garður can be garden or sometimes yard, depending on context

So there is not just one possible natural English version.