Hún spurði hvaðan ég væri að koma þegar ég kom seint.

Hvaðan means from where, while hvar means where.

So:

• hvaðan ég væri að koma = where I was coming from
• hvar ég væri = where I was

Because the sentence is asking about the origin of the movement, Icelandic uses hvaðan.

Væri is the past subjunctive of vera (to be).

In Icelandic, indirect questions and reported speech often use the subjunctive, especially after verbs like spyrja (to ask), segja (to say), and similar verbs.

So:

• Hún spurði: Hvaðan ert þú að koma? = direct question: She asked: Where are you coming from?
• Hún spurði hvaðan ég væri að koma. = indirect question: She asked where I was coming from.

A learner coming from English often expects an indicative form here, but Icelandic commonly prefers the subjunctive in this kind of subordinate clause.

Here vera að + infinitive is a common Icelandic way to express an ongoing action, similar to the English progressive.

So:

• ég er að koma = I am coming / I’m on my way / I’m coming right now
• ég var að koma
• ég væri að koma

In this sentence, ég væri að koma means something like I was coming or I was in the process of coming.

The að is simply part of this construction. It is not the same as English to in a literal word-for-word sense, even though it looks similar.

They are doing different jobs.

• væri að koma describes an ongoing action in the subordinate clause: where I was coming from
• kom is the simple past of koma and refers to the event of arriving: when I came/arrived late

So although both come from koma, they are used differently:

• vera að koma = be coming
• koma in the simple past = came / arrived

This is very natural in Icelandic.

Because this is a subordinate clause, not a main clause.

In Icelandic main clauses, the verb often comes in second position. But in subordinate clauses introduced by question words or conjunctions, the order is usually more like:

question word + subject + verb

So:

• main question: Hvaðan ertu að koma? = Where are you coming from?
• subordinate clause: hvaðan ég væri að koma = where I was coming from

That is why ég comes before væri here.

Spurði is the past tense of spyrja, which means to ask.

So:

• ég spyr = I ask
• hún spurði = she asked

The subject hún means she, and spurði agrees with that subject in person and number through the verb form.

Icelandic does not always need to include the person being asked if the meaning is already clear from context.

So:

• Hún spurði hvaðan ég væri að koma = She asked where I was coming from
• Hún spurði mig hvaðan ég væri að koma = She asked me where I was coming from

Both are possible. Adding mig makes the object explicit, but it can be left out.

Þegar means when here and introduces a time clause.

So:

• þegar ég kom seint = when I came/arrived late

It tells you the time at which she asked the question.

The sentence structure is:

• main clause: Hún spurði ...
• subordinate clause 1: hvaðan ég væri að koma
• subordinate clause 2: þegar ég kom seint

In natural English, this is usually best understood as arrived late.

The verb koma often means come, but in many contexts it is used where English would naturally say arrive.

So:

• ég kom seint = I came late literally
• but more naturally: I arrived late

That is a very common usage.

Because seint is an adverb here, modifying the verb kom.

It tells us how or in what way the person came/arrived:

• koma seint = to come late / arrive late

If you used an adjective instead, it would describe a noun, not the action.

Not always exactly, but it is often close.

The Icelandic vera að + infinitive covers an ongoing or immediate action, and depending on context it can translate as:

• was coming
• was on my way
• had been coming
• sometimes simply came from, depending on what sounds natural in English

So in this sentence, hvaðan ég væri að koma is most naturally understood as where I was coming from.

Yes:

• Hún = she
• spurði = asked
• hvaðan = from where
• ég = I
• væri = were / was (subjunctive of vera)
• að koma = coming / to come, here as part of vera að koma
• þegar = when
• ég = I
• kom = came / arrived
• seint = late

So the structure is very roughly:

She asked [from where I was coming] [when I arrived late].

Grammatically, var að koma would be possible in some contexts, but it would not be the most typical choice here.

After spurði in an indirect question, Icelandic often uses the subjunctive:

• Hún spurði hvaðan ég væri að koma is the expected standard pattern.

Using var would sound more like a straightforward factual statement rather than reported-question style. For learners, the safest takeaway is:

• after spurði
  • indirect question, expect the subjunctive very often.

Ég is nominative, because it is the subject of both clauses where it appears:

• ég væri að koma
• ég kom seint

Even though the sentence is embedded inside other clauses, ég is still the subject, so nominative is correct.

Yes, it is natural, especially in the way it uses:

• hvaðan for from where
• the subjunctive væri in an indirect question
• vera að + infinitive
• kom seint for arrived late

A very slightly fuller version could also be:

Hún spurði mig hvaðan ég væri að koma þegar ég kom seint.

But the original sentence is perfectly good Icelandic.