Ég set húfuna á mig þegar það er kalt úti.

Set is the present tense of setja, which basically means to put, place, set.

So Ég set húfuna á mig literally means I put the hat onto myself, and in natural English that becomes I put on the hat.

In this sentence, the present tense can describe:

• a habitual action: I put on the hat when it’s cold outside
• a general tendency: I wear/put on the hat when it’s cold outside

So even though the verb is literally put, the whole phrase functions like put on in English.

Because húfuna is the definite accusative singular form of húfa.

Here is the breakdown:

• húfa = a hat / hat
• húfan = the hat in the nominative
• húfuna = the hat in the accusative

It is accusative because húfuna is the direct object of set.

So:

• Ég set húfu á mig = I put on a hat
• Ég set húfuna á mig = I put on the hat

A very common thing for English speakers to notice is that Icelandic usually puts the definite article at the end of the noun instead of using a separate word like the.

Because á takes different cases depending on whether there is motion/change or location/state.

In this sentence, the hat is being moved onto the speaker, so Icelandic uses the accusative:

• á mig = onto me

Compare:

• Ég set húfuna á mig. = I put the hat on me.
  
  • movement → accusative
• Húfan er á mér. = The hat is on me / I am wearing the hat.
  
  • location/state → dative

This motion-vs-location pattern is very important with Icelandic prepositions.

Because sig is only the reflexive form for the third person.

For the first person, Icelandic uses the normal pronoun:

• mig = me
• þig = you
• sig = himself / herself / itself / themselves in reflexive use

So:

• Ég set húfuna á mig. = I put the hat on myself.
• Þú setur húfuna á þig. = You put the hat on yourself.
• Hann setur húfuna á sig. = He puts the hat on himself.

English speakers sometimes expect a special reflexive in all persons, but Icelandic only has this special reflexive form in the third person.

It is understandable and natural enough, but Icelandic has a few different ways to talk about putting on clothes.

Possible alternatives include:

• Ég set á mig húfu þegar það er kalt úti.
• Ég set upp húfu þegar það er kalt úti.
• Ég fer í húfu þegar það er kalt úti.

The differences are small and depend on style and context:

• setja á sig = literally put onto oneself
• setja upp is often used with things like hats, glasses, etc.
• fara í is very common for put on clothes

Also, húfuna means a specific hat, while húfu can sound more general: a hat / a hat in general.

So if you mean a general habit, many speakers might prefer something like:

• Ég fer í húfu þegar það er kalt úti.
• Ég set á mig húfu þegar það er kalt úti.

Þegar means when.

It introduces the time clause:

• þegar það er kalt úti = when it is cold outside

So the sentence has two parts:

• Ég set húfuna á mig = main clause
• þegar það er kalt úti = subordinate time clause

This is very similar to English structure.

Here það works like it in English weather or condition expressions.

So:

• það er kalt = it is cold

This það does not refer to a specific thing. It is a grammatical subject, just like English it in:

• It is cold
• It is raining
• It is dark

So Icelandic and English are very similar here.

Úti means outside or outdoors.

So:

• það er kalt úti = it is cold outside

It is an adverb, and putting it at the end is very normal.

You can compare:

• inni = inside
• úti = outside

Examples:

• Það er hlýtt inni. = It is warm inside.
• Það er kalt úti. = It is cold outside.

Yes. Icelandic word order is flexible, but there are rules.

The original sentence is:

• Ég set húfuna á mig þegar það er kalt úti.

You can also put the þegar-clause first:

• Þegar það er kalt úti, set ég húfuna á mig.

Notice what happens: in the main clause, the verb comes before the subject after the opening clause:

• set ég not
• ég set

That is because Icelandic is a V2 language in main clauses: the finite verb usually comes in the second position.

So this is a very useful pattern to learn.

Yes. Very often, Icelandic present tense works like English simple present for habits and general truths.

So this sentence most naturally means something like:

• I put on the hat when it’s cold outside
• I wear/put on a hat when it’s cold outside
• When it’s cold outside, I put on the hat

It does not have to mean that the speaker is putting on the hat at this exact moment.

If you wanted to make it clearly about right now, you would usually add context, for example:

• Ég er að setja húfuna á mig. = I am putting the hat on.

Yes. That is also possible.

Both of these are natural:

• Ég set húfuna á mig
• Ég set á mig húfuna

The difference is mostly one of emphasis and rhythm.

Very roughly:

• Ég set húfuna á mig puts the object húfuna earlier
• Ég set á mig húfuna keeps the phrase á mig close to the verb

Learners should understand both patterns when they see them. Icelandic often allows this kind of variation, especially with short pronouns and prepositional phrases.

Because Icelandic usually expresses the by attaching it to the noun as a suffix.

So:

• húfa = hat / a hat
• húfan = the hat
• húfuna = the hat in the accusative

This is one of the biggest structural differences from English. Instead of saying a separate word like the hat, Icelandic often builds the definiteness directly into the noun form.

That is why learning noun forms with case endings is so important in Icelandic.