Um kvöldið byrjar þrumuveður, og við sjáum eldingar fyrir ofan húsin.

Um kvöldið is a time expression meaning in the evening or that evening, depending on context.

• um is a preposition often used with expressions of time
• kvöldið is the evening

So literally it is something like during the evening.

This is a very common Icelandic way to set the time frame at the start of a sentence.

Because kvöldið is the definite form: the evening.

• kvöld = evening
• kvöldið = the evening

In Icelandic, the definite article is usually attached to the end of the noun rather than written as a separate word. So instead of a separate word like English the, Icelandic often adds an ending.

Here, Um kvöldið gives a more specific feeling: that evening / in the evening.

It is in the accusative.

The preposition um normally takes the accusative when it means around, about, or when used in many time expressions. So:

• nominative: kvöldið
• accusative: kvöldið

In this noun, nominative and accusative happen to look the same, so you do not see a change in form here.

This is because Icelandic usually follows a verb-second pattern in main clauses.

The sentence begins with Um kvöldið, which takes the first position. After that, the finite verb usually comes next:

• Um kvöldið byrjar þrumuveður

So even though þrumuveður is the subject, the verb byrjar comes before it because the time phrase is in first position.

This is very normal in Icelandic and is something English speakers often need to get used to.

Yes, þrumuveður is one word, and it means thunderstorm.

It is a compound noun:

• þruma = thunder
• veður = weather

So it literally suggests thunder-weather.

Icelandic forms many nouns this way, by combining smaller words into one compound.

Byrjar is the 3rd person singular present form of byrja, meaning to begin.

Here the subject is þrumuveður, which is singular, so the singular verb form is used:

• ég byrja = I begin
• þú byrjar = you begin
• það byrjar = it begins

Since þrumuveður is a singular noun, Icelandic uses byrjar.

Because the sentence is introducing the storm in an indefinite way: a thunderstorm begins or there is a thunderstorm starting.

• þrumuveður = a thunderstorm / thunderstorm
• þrumuveðrið = the thunderstorm

If you used þrumuveðrið, it would sound like a specific thunderstorm already known from the context.

Sjáum is the 1st person plural present form of sjá, meaning to see.

• ég sé = I see
• við sjáum = we see

So:

• við = we
• sjáum = see

This is an irregular verb, so learners often need to memorize its forms rather than predict them from a regular pattern.

Eldingar is in the accusative plural because it is the direct object of sjáum.

We are seeing lightning flashes or lightning bolts, so eldingar is the thing being seen.

For this noun, the plural form eldingar can serve as nominative plural and accusative plural, so again the form does not visibly change here.

Because Icelandic often uses the plural when talking about visible lightning flashes: lightnings / lightning bolts / flashes of lightning.

In natural English, we usually just say lightning, but Icelandic commonly uses the countable plural eldingar when referring to separate flashes seen in the sky.

So the grammar reflects how Icelandic naturally packages the idea.

Fyrir ofan means above or up over, often with a clear sense of position.

• fyrir ofan húsin = above the houses

Yfir can also mean over/above, but it can sometimes feel broader and can also suggest movement across or over something, depending on context.

In this sentence, fyrir ofan works well because the point is simply where the lightning is visible: above the houses.

Because after fyrir ofan, Icelandic normally uses the accusative when describing position in this kind of expression.

So:

• húsin = the houses (accusative plural, also same as nominative plural here)

Húsunum is the dative plural form, and that is not the form expected here.

Since hús is a neuter noun, some of its forms are identical, which can make it a little confusing at first.

Húsin means the houses.

The definite form makes sense because the speaker probably has specific houses in view — the houses in the scene being described. Icelandic often uses the definite form when referring to visible or contextually known things.

• hús = houses / house
• húsin = the houses

So the sentence is not just talking about houses in general, but the particular houses below the lightning.

It can be. Icelandic punctuation often allows a comma between two main clauses, especially when each clause has its own verb:

• Um kvöldið byrjar þrumuveður
• og við sjáum eldingar fyrir ofan húsin

Since both parts are full clauses, the comma is natural and common. In English, usage can vary, but in Icelandic this kind of comma is very normal.

A few points that often help English speakers:

• þ in þrumuveður is like the th in thing
• ð in kvöldið and veður is like the th in this, though in real speech it can be softer or less fully pronounced
• sjáum begins with sj, which sounds somewhat like sy to English ears
• au in sjáum is a diphthong, not a simple English aw

Also, Icelandic stress usually falls on the first syllable of the word:

• KVÖL-dið
• ÞRU-mu-veður
• SJÁ-um
• EL-ding-ar

That first-syllable stress is one of the most important pronunciation habits to build early.