I morse var det så mycket dimma att vi knappt såg huset mittemot.

I morse means this morning or earlier this morning.

It refers specifically to the morning of the current day. By contrast, på morgonen usually means in the morning in a more general sense, or during the morning.

So:

• I morse = this morning
• På morgonen = in the morning

In this sentence, i morse is used because the speaker is talking about what happened earlier today.

This is because Swedish follows the V2 rule in main clauses. That means the finite verb must come in the second position.

Here, I morse comes first, so the verb var must come second:

• I morse var det så mycket dimma...

If you started with det, then you would say:

• Det var så mycket dimma i morse...

Both are correct, but the word order changes depending on what comes first.

Here det is a kind of dummy or formal subject, similar to English it in sentences like It was very foggy or There was a lot of fog.

Swedish often uses det in weather expressions and general statements:

• Det regnar = It is raining
• Det var kallt = It was cold
• Det var mycket dimma = There was a lot of fog

So det does not refer to a specific thing. It is just needed to make the sentence work grammatically.

Swedish can express this idea in more than one way.

This sentence uses a noun phrase:

• så mycket dimma = so much fog

That is very natural in Swedish. Another possible way would be:

• Det var så dimmigt att... = It was so foggy that...

Both are correct, but så mycket dimma focuses on the amount of fog, while så dimmigt describes the condition more directly.

Because dimma here is treated as an uncountable noun, like fog in English.

With uncountable nouns, Swedish uses mycket:

• mycket vatten = much water
• mycket snö = much snow
• mycket dimma = much fog

Många is used with countable plural nouns:

• många hus = many houses
• många bilar = many cars

So så mycket dimma is the correct choice.

Så ... att means so ... that.

It is used to show a result:

• så mycket dimma att vi knappt såg huset = so much fog that we could barely see the house

This structure is very common in Swedish:

• Det var så kallt att vi stannade inne = It was so cold that we stayed inside
• Hon var så trött att hon somnade direkt = She was so tired that she fell asleep immediately

So in your sentence, the fog was strong enough to cause the result that they could hardly see the house.

Knappt is an adverb meaning hardly or barely. In Swedish, sentence adverbs and similar adverbs often come before the main verb in a clause like this.

So:

• vi knappt såg huset

is the natural order here.

Compare the English structure:

• we barely saw the house

Swedish and English are quite similar in this case, although Swedish adverb placement can vary depending on the sentence type.

Såg is the past tense of se, which means to see.

Forms:

• infinitive: se
• present: ser
• past: såg
• supine: sett

So:

• vi såg = we saw
• vi knappt såg = we barely saw

This is an irregular verb, so it is worth memorizing.

Huset is the definite form, meaning the house.

The sentence is talking about a specific house, namely the one opposite them. Swedish often uses a definite noun where English would also use the:

• ett hus = a house
• huset = the house

Because the house is identified further by mittemot, it is natural to use the definite form:

• huset mittemot = the house opposite / the house across from us

Mittemot means opposite, across from, or directly facing.

In this sentence:

• huset mittemot = the house opposite
• more naturally in English: the house across from us

It can be used in a few ways:

• Huset mittemot är gult = The house opposite is yellow
• Hon bor mittemot oss = She lives across from us

Here it acts almost like a post-position, coming after huset.

Swedish often leaves that unstated when it is obvious from context.

So:

• huset mittemot

naturally means the house opposite or the house across from us/across from where we were.

If you want to be more explicit, you could say:

• huset mitt emot oss = the house opposite us

But in many everyday situations, just huset mittemot is enough.

Yes. You may see both mittemot and mitt emot.

In modern Swedish, mittemot as one word is very common, especially in standard written language. Mitt emot also occurs and means the same thing.

So these are equivalent:

• huset mittemot
• huset mitt emot

For a learner, it is useful to recognize both spellings.

Yes, several alternatives are possible. For example:

• Det var så mycket dimma i morse att vi knappt såg huset mittemot.
• I morse var det så dimmigt att vi knappt såg huset mittemot.

These mean nearly the same thing.

The original sentence puts i morse first for emphasis on time, and så mycket dimma emphasizes the amount of fog.